# Kevin - A V Carroll Horizontal Mill Rebuild



## durableoreo (Aug 21, 2020)

(Some of this was posted on Practical Machinist but I eventually figured out that those guys are more serious than I am.  So updates will only be posted here.)

Purchased a small horizontal mill recently.  It's labeled "A V Carrol" and . I'm getting it ready to make chips.  It was fairly cheap but it came with quite a few issues, including lever-feed on the x- and z-axis.  There's still flaking on the ways, which is nice to see.  The x-axis is a bit worn but I can live with it.

Decided to get the arbor off.  Partly to figure out how it all goes together, partly because I want to make another arbor for 1-1/4 cutters.  Eventually I figured out that there's a drawbar that was bottomed out in the threads of the arbor but there was still about 1/16 end play.  I'll add another spacer when I put it all back together.  

Here's the starting point, the mill in all its dirty factory-use glory.  It's one of those small single-operation type mills for small parts, so the table is about counter height.  It's a lot smaller than I expected, which is perfect because the shop space is about 50 sq-ft and there's already a 9x20 lathe and a drill press in there.






Here's both sides views of the spindle.  









Closer view of the working end of the arbor.  Note the keyway is not lined up with the set screw hole because I was messing with it.  There's a matching flat on the arbor.  The bearing is mounted in this little cylindrical mount/enclosure.  It's a tapered roller bearing that's tensioned from the back, so the bearing assembly is sealed by that cover but the cover is held on with t-slot nuts---the screws sticking out aren't studs going back to the main casting.  The bearing enclosure bears against the main casting and is connected with grub screws.  I might add some 1/8 pins because there's quite a lot of play in the shaft, even after pre-loading the bearings.





Closer view of back end of arbor.  The arbor has some damage from the set screw but it's a fairly thin-walled tube at this point so it's more of a dent, no burrs that I could feel with a stone.  The handwheel came off without trouble.  





Not sure about that groove in the drawbar.  On the right side, you can see the driven axis, which is a threaded 1-1/8 tube.  There's a tapered roller bearing in there and the big lump there  (first 2 steps) is a retaining/tensioning nut with fairly fine threads with a heavy bushing (3rd step) that transfers compression from the nut to the inner cone of the bearing .  When I removed all those parts, the arbor still wouldn't come out.





Here are images of the make/model.  I haven't been able to find information about anything other than lathes that were produced by A V Carroll.  I could have sworn there was another thread I started back when I was in rigging mode... Anyway, someone pointed out that machinery companies sometimes re-sell models that they don't directly produce, for business reasons.  I noticed that the base is fairly generic and the only other place the manufacturer's name appears is a removable cover---easy to re-brand.  So if anyone recognizes the castings, I'd be glad to know more about the manufacturer.  It would be so great if I could find another arbor.









The plan... It's too much, as usual.  But I'll start with the most important things.

First, I need to re-power the mill.  It's running 1:1 with a 1750-RPM induction motor, which is 20-30 times too fast.  With a 3" HSS cutter, I need 25-100 RPM to hit reasonable feed rates (20-80 SFM for annealed low-carbon steel, according to my non-machinist reading of the 24th edition handbook).  I might use some carbide cutters, so I knew I would need a high and low range.  I would love to use a variable-drive type system but I just don't have the chops for that yet.  So I'm falling back on a variable speed electric motor.  I made a spreadsheet and figured I would need a 1:5 and a 1:10 reduction to get in the ballpark.  Those ratios are pretty large and on the verge of impractical for v-belts, especially with the space constraints.  Eventually, mostly by luck, I figured out that a 1:15 gearbox and a pair of pulley ratios (1:2.5 and 2.5:1 would be good.  Also, I want the 1:15, so I can run the motor at half speed or more.  I should be able to do it with 1 belt, switching it between 3 sets of pulleys.  I tried to find ready-made stuff but for 1-1/8 bore with keyway, finding a step pulley with 5", 2" and whatever 1:1 is for the same belt length, that's about impossible.  Plus, a 5" pulley may not quite fit.  It's hard to know because the casting is rough and I don't know how to measure it properly.  I think I'll buy blanks at McMaster, bore 1 of them, and do a trial fit.  If I need to make it smaller to fit, I can adjust the 2" pulley smaller, too.  For 3L belts, a 2" pulley (or a little less) should be OK.  I have a 1-1/2 pulley for 3L sitting on my desk.  It's extreme but possible.  So that's the plan.  Got a planetary gearbox on the way from Apex Dynamics (AB115) and materials for the pulleys and idlers will be here in a few days.

For the motor, I'll start with a sewing machine "servo" which is cheap and maybe works.  There's a maximum speed dial (350-3500 RPM) and there's a pedal input with brake.  No specs, though.  I took it apart to figure out what was going on.  The motor is brushed.  Sewing machines need good torque at low speed so it's probably a series-wound dc motor.  There's different speed control methods and I have no idea what it has.  There is a switch to change direction and the throttle (pedal input) is a hall sensor.  I did some stall-speed torque testing to convince myself that this wasn't a fools errand.  I noticed that when the maximum speed was set low, torque was low.  So I think I'll set it on maximum and use the throttle to set the speed.  I'd like to mount the various controls remotely so I can operate the machine from the front and with a minimum of fuss.

After the mill is re-powered, I'll need to address the x- and z-axes, which were lever operated.  It's a good system but a rack-and-pinion situation won't work for me.  I want power x feed and finer control of z motion.  The x-axis will be fairly easy to switch over to a 1/2-10 acme screw.  The z-axis... It's a little harder to imagine.  There are features on the castings (pan and knee) that seem perfect for installing a lead screw.  So maybe it won't be so hard.  Haha.  Who am I kidding?


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## NortonDommi (Aug 21, 2020)

That is a very solid looking machine. If you are going to change pulleys have you thought about multi-V ones? Lower profile than V-belts, can transmit more torque, run quieter, they can also be used on smaller pulleys than V-belts allowing a great range of ratio in tight quarters.
Beauty of a rebuild with mods is you can do whatever you want within reason. A gearbox is a great idea!  What sort of H.P. are we looking at here?


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## durableoreo (Aug 21, 2020)

NortonDommi said:


> That is a very solid looking machine. If you are going to change pulleys have you thought about multi-V ones? Lower profile than V-belts, can transmit more torque, run quieter, they can also be used on smaller pulleys than V-belts allowing a great range of ratio in tight quarters.
> Beauty of a rebuild with mods is you can do whatever you want within reason. A gearbox is a great idea!  What sort of H.P. are we looking at here?



The multi-groove belts are a good idea.  Let me have a look...  I might need the low profile and tighter bend radius.

The mill came with a 1/3 HP motor.  The motor I'm going to try is rated for 550 W, which is about 3/4 "HP".  Not sure if that is an honest number.  Barker mills (they still make them) have a 1/3 HP series (PM) and a 2 HP series (AM).  I suspect the castings are the same but they put a bigger motor in them depending on the type of work that is to be done.

The gearbox was about 200 $ so I hope it works out!


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## DiscoDan (Aug 21, 2020)

I have a very similar small horizontal Mill. Mine is a Pratt & Whitney from World War II. Mine is powered by a variable speed Craftsman motor. Makes it very easy to set up. If you can find one


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## durableoreo (Aug 23, 2020)

That looks great.  You're right, that would make it easy!  I've seen some with fancy gearhead motors, too.

I started looking at http://lathes.co.uk/ which has pictures of many historical mills.  There are so many of these things...  I haven't found anything that's quite the right shape


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## durableoreo (Aug 23, 2020)

Here are some more details about the spindle speed.  It's based on Machiner's Handbook numbers for upper and lower spindle speeds. 







Here's what you get if you reduce a 3500-RPM motor 15:1 then step up or down by 2.5 to get a medium, high, and low range.  I'm suspicious about using the motor at the lower RPMs because I suspect that torque will be lower.  But with 3 speed ranges, I can get most speeds in the upper speed range as long as I stay in the box.  I can experiment with the lowest ranges but I don't need it for normal mill operations.  For really large cutters on a hard shaft or slotting, going below 50 RPM might be useful.


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## durableoreo (Aug 23, 2020)

I also purchased a 3-axis DRO and RPM meter.  It was 276 USD.  Matching green, for vanity.  I seriously considered buying sensors and hacking together an Arduino.  Decided against it, in the end, because I'm trying to quit.  It's satisfying to do things yourself but it all takes time.  The side-to-side travel is the most, at 12" and about 3.25" in the other direction, towards or away from the operator.  The vertical axis is 6".  Probably could have gotten away with a 2-axis DRO and a caliper but it's almost easier to have a single system






Now, I'll need to figure out how to mount the display. I'll need another panel with various other controls, too, mounted near the DRO.  I want it to be sturdy and not retreat from my fingers.  I could make a 3-point mount, contacting each of the 3 corners of the table.  Or mount it on the back corner so it swings wide and have a hook that catches on the front corner.  I want it sturdy but not in the way when I'm changing belts.  Normally screens are meant to be mounted so that the top of the screen is eye level.  But this mill is fairly small so having the display that high might produce unnecessary moments and look/feel weird.  Proportion may be more important than slavishly following ergonomics rules for desktop computers.

I need a a switch for the motor, a throttle for the motor, tachometer, and switches for auxiliary lighting and coolant pump.  (There's no coolant plans at the moment but I might do that for the future, especially if I want to cut harder materials.)  A panel below the DRO seems like a good place for those.

When changing belts, it's best to have 2 switches to prevent accidents.    Ideally, unplugging the equipment is the solution.  I'm fairly conscientious but I can't get myself to unplug machines when making adjustments.  And in industrial equipment, it's not possible to disconnect equipment from the mains.  Instead, interlocks and E-stop circuits prevent workers from accidentally engaging the equipment during maintenance.  For this application, 2 switches in series seems like a good solution.  A switch up by the DRO for normal use and a 2nd motor switch near the access panel for changing belts.  My first thought was a toggle inside the main casting.  But it would be convenient if it were activated by the removal of the cover... Maybe a reed switch.  But the magnet probably can't be mounted directly on the cast iron cover---maybe use a bit of phenolic resin or wood as a spacer.  And a reed switch can't carry enough current so I need a relay... Also, I want the motor power switch on the panel to turn off if there's a loss of power, so I need a latching switch there.  Maybe the coolant pump needs a latching switch, too.  This is getting complicated.  I stopped to consider that I'm getting greedy with features.  After some consideration, I decided that A DRO, tachometer, and basic safety interlock isn't too much to ask of a mill.


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## durableoreo (Aug 24, 2020)

Well, I'm thinking about feeds.  I want power feed on the x axis.  Probably z, too, but the x-axis is more important because it will be one of the factors that effects finish.  Below is a spreadsheet that addresses cutter RPM and the amount of bite from each tooth.  It's based on Machiner's Handbook.  I intend to run smaller endmills on occasion, so that's included in the table.  It's tricky because feed rate depends on the size of the cut, which depends on materials, diameter of the cutter, number of teeth on the cutter, and the RPM of the spindle.  I calculated feed (IPM) for combinations of maximum and minimum spindle speeds and max/min feed-per-tooth rates.  There's a lot of room for variation so I plugged in diameters and tooth counts for cutters I have in-hand.






It's hard to get a good idea of what's needed so I plotted all the results.  Looks like feeds can be as low as 0.2 to 275 IPM.  That's 4 orders of magnitude and I can't afford another fancy gearbox.  If I only consider HSS cutters with diameters between 2 and 4.5, the range is 0.2 to 42, which is more reasonable.  Oh, I found the manual for the Cincinnati dial-type universal mills.  They had feeds from 1/2--40 IPM, in a high and low range. OK, so if the standard in universal milling machines uses a range of 0.5-40 IPM, that's good enough for me.  The bad news is that even this reduced range is still basically 2 orders of magnitude, or 80:1.  For the spindle, we only needed about 40:1 plus variable speed motor, which is relatively easy.  So what to do?  

First I looked at commercial power feed units.

There's a unit that Little Machine Shop sells.  It's about 400 $ US and I couldn't find any information about it's max/min speeds, torque, etc.  

There's an eBay special, 100% Chinesium, which I tried to ignore.

Saw lots of DIY power feed solutions.  Stefan Gotteswinter builds a nice one out of a windshield-wiper motor.  It needs a clutch because of the worm-gear reduction, which I don't want to make or buy.  With the gearbox, typical output would give me 6 in/min.  Speed control might give me 0.5 in/min but I doubt the torque would be adequate.  Well, those motors usually put out 30--50 ft-lb of torque, so it might be OK.  With a 2:1 reduction in a pulley drive...  But then you're limited to a maximum speed of 3 in/min, which isn't what I want, either.

MyfordBoy made a nice power feed system using a stepper motor that's rated for 425 in-oz.  He runs it on a big vertical mill.  I like this solution the best but I can't fit that motor on my tiny mill.  There's simply nowhere to put it.  I would need to make or buy a right-angle gearbox.  Also, it's fairly heavy. 






The eBay power-feed offering claims 150 ft-lb of torque and 0-200 RPM, which sounds good; that's 0-20 in/min.  The problem is that I don't believe that the torque is enough at low speeds and I'm not sure that the system will run at 0.5 in/min.  Then, by luck, I found a review on the Build Something Cool channel, (YouTube) where Dale tests out this cheap item compared to 4 others.  The slowest this unit will go is 0.150" in 10 seconds, which is 0.9 in/min. 

Maybe I can live with 0.9 in/min.  If you look at the table, most of the less-than-unity speeds are in the Min/Min category. It account for about 12% of the cases.  Honestly, I don't have the experience to say if these are important.  I suspect that I will be giving up milling very hard materials---shafts that are so hard that I need slow spindle speed AND because of inadequate stiffness in my machine, I need to have slow feed. Or perhaps buy the right cutter, one with smaller diameter and fewer teeth.  

There are 27% of cases that are too high to accommodate with the Ding-Wang unit.  Almost all of these are in the Max/Max category for carbide tooling.  That is, maximum spindle speed with the maximum feed rate.  I do not anticipate needing this particular category because I'm limited in spindle power and rigidity. 

So, it's a compromise but it only cost 125 $ US.  It will arrive in a few days.  Unfortunately it weighs 14 lb, which is a lot for my little mill.  And it's a chunky monkey.  I hope it doesn't end up looking too weird.

Here's the cases that the Wing-Ding unit covers, if connected 1:1 to the 1/2-10 leadscrew for the x-axis.  They're in green.  






What if I stepped it down a bit?  As I reduce the lower speed, the upper speed is also reduced, so it's not clear if this will results in more or fewer cases being covered.  I chose some ratios and counted the number of cases that are covered (feeds between upper and lower limit).  As the ratio decreases, the number of cases covered goes down.  If I step it up, the coverage is better but I lose all the Min/Min cases for HSS tools.  So I think direct drive (1:1) is probably the way to go.






Finally, the most basic aspects of the mill are determined.  If I had bought a Grizzly horizontal mill, this would all be taken care of.  Sounds, nice, actually.  But from the reviews, I've heard that the G0727 doesn't have low-enough speeds, so maybe it wouldn't be nice at all.  I think they had to make some sacrifices in the cartridge spindle to allow larger cutters and smaller endmills.


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## durableoreo (Aug 24, 2020)

Now, it's time to make pulleys.  Turns out, the specifications are fairly simple.  First, if a belt fits a pulley, it does not touch the root of the groove in the pulley.  It can protrude beyond the outer rim of the pulley.  For small pulleys, under 2-1/4 inches in diameter, included angle is 34 degrees and the width at full diameter should be 0.494 for A belts.  This is from Machinery's Handbook, 24th Ed.  As pulleys get larger, the angle increases so that pulleys over 4-1/4 are angled at 38 degrees.  After reading through all this stuff, I'm impressed with the complexity of the mechanical world.  I had previously though of belts as obvious and old tech that was simple.  But if you get into the shape of the belt, finding the pitch line, the details of the pulleys, how the belts age and the effects on efficiency of the drive---it's more complex than I thought.  And there's also flat belts, narrow v-belts, and ribbed v-belts to consider.

The casting around the spindle does not give me a lot of clearance.  I considered switching from 3L (3/8 wide, a size below A) to a grooved belt.  They don't have the wedging action of a v-belt so they can be run at a higher tension.  Also, the profile of the pulleys is less and smaller pulleys are possible. Also, I think they would be easy to make with a form tool.  I wouldn't have any reason to get out the terrible compound that came with my lathe.  After searching for what's available, I found that I was going to need to make the pulleys wider than the stock I had purchased.  Has to do with how much horsepower per rib the belt can support.  So I'm going back to 3L.  Those belts are available at McMaster in 1-inch increments.  In sizes around 27" they're available in 1/2-inch increments, which is convenient.

So how long of a belt do I need?  I took some measurements and made a spreadsheet.  Instead of calculating the exact length, I'm assuming that half the diameter D/2 at each pulley, except the idler on the tensioner, which was D/3.  Then use the distance between pulley centers to estimate the belt spans between pulleys.  Then I made a table in which the first row represented a 2.5:1 pulley ratio (5" and 2" pulleys) and the corresponding belt length.  Then I calculated the belt length for 5" and 5" pulleys, then 4.75" and 4.75, etc, decrementing pulley diameter by 0.25" for each row.  Eventually, I found that a pair of 3.5" pulleys requires the same belt length as the other steps in the pulley.  So now I can make my custom step pulleys---5, 3.5, and 2".  This is all depending on being able to get a 5" pulley in there.






I did the same analysis assuming I need to cut down the largest pulley to 4.5", which requires 1.8" to get a ratio of 2.5:1.  The 1:1 pulleys for that length of belt is 3.25.  Here's the table for that:






I also need a tensioning mechanism.  I'd like an over-center mechanism that uses the belt tension to hold it in place and the operator can feel the tension directly.  As much as I'd like something fancy, a tiny masterpiece, I should probably resist the urge and do something simple.  Making speed changes easy is part of the psychology and I want to stick to that.  Moving the belt should not require tools, fiddling, or brute strength.  Well, whatever the mechanism, there's another hole in the back of the mill that I plan to use.  Not sure what it was for.  The original tensioner is that bar on the left, which does not rotate because it was set with millwright strength.  It's held in position by a 3/8 bolt and nut.  Despite a 7" lever arm, it holds tension.  Maybe they were only taking very light cuts... looks flimsy to me.


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## durableoreo (Aug 27, 2020)

Plans have changed.  I was reading about the 15-$ DC-motor speed controlers on eBay... they don't control RPM so the speed will dip under load.  Maybe I'm being fussy but I just want steady speed.  Can you imagine setting the RPM during a pass only to have the speed double when you complete the pass and the mill has no load?  Can you start the approach to your next pass with the RPM zipping along so the teeth first encounter the work at high speed?  Doesn't seem like a good idea to me.

So I purchased a 1-HP three-phase motor, used.  It runs at 1750 but I was careful to get an induction motor so I should be able to spin it at 2x, which is the top speed for the transmission I designed.  I also purchased a S70 VFD, which was amazingly cheap.  Maybe I should have done this in the beginning without bothering with gears and pulleys.  I just didn't know enough to decide.  I also didn't realize how fantastically inexpensive this type of setup could be.  But I'm going to stick to my transmission design for now because I don't know about torque at very low motor speeds.  Perhaps it is possible to run fairly slow but perhaps heat or something else is an issue.  If I can run the motor near its rated speed, I'll get 300, 120, or 47 RPM, depending on the belt position.  See the color coded boxes in the chart below.  The box is what I expect to use most of the time.  Overspeeding the motor is probably OK---the practical machinists say 150% to 200% is find for induction (squirrel-cage) motors.






I cut some pulleys today.  There's nothing like doing something new to realize how much you don't know.  I bought 1/2" rounds from McMaster and thought the rest would be fairly easy.  But it turns out that my chuck can hold nothing larger than 3.9" so I had to figure out a work-holding strategy for the 4" and 5" stock.  And then I discovered that the inside jaws on my chuck could grip the 1.25" IDs of half the pulleys but not the 1.125 IDs of the other half.

For the 2" pulleys, I was able to grip the work in the chuck and bore out 1.25 and 1.125" holes.  Then using those holes, grip them from the inside and cut the groove.  For the small pulleys, it was 32 degrees, or 17 degrees per side.  I did the setup with a protractor.  Testing the belt, it's fairly important that the belt rides at least 2/3 deep in the groove and that it not touch the root of the groove.






The larger parts I had to bore on the faceplate.  Instead of using a set of clamps, I drilled and tapped 1/4-20 holes in the face plate and drilled clearance holes in the blanks.  Then, secured to the faceplate with some machine screws, I was able to bore out the center of the 3.5" and 5" pulley.  
I was able to grip some of the pulleys (1.25" ID) in the chuck.  Then it was the usual operations---face off, true the pulley, break the edges, and cut the angled groove.  






The other pulleys won't fit on the chuck so I think I'll make a stub shaft with a tapped hole in the end.  Haven't decided but I'll show a picture of what I end up doing.

I think that took me 6 hours between trying to decide what to do and doing it.  My lathe is marginal, at best, and I'm not an experienced machinist.  If I had paying work, I would love to replace it with something less janky.  I know it can be improved but I don't have the patience to thread the belt this way and that, to change gears, etc.  But, in the words of AvE, you've got to **** with the dick you have.


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## durableoreo (Aug 28, 2020)

The pulleys with 1.125" ID wouldn't fit on the jaws of my chuck.  Was thinking of making a mandrel.  Instead, I turned down the jaws of the chuck about 0.010".  I know, it's terrible practice and just shouldn't be done but it saved me so much time.  The jaws were reasonably hard so I turned the chuck by hand and used a brazed carbide cutter.

The pulleys are bored and the V is cut.  Took forever.  Probably 8 hours for the first 3, including all problems solved along the way.  The second set and the idler triple pulley took more like 4 hours.







The set that go on the 15:1 planetary gearbox output shaft need a keyway.  The set that go on the spindle also need a keyway but I have a trick up my sleeve.  The front bearing of the spindle is covered in the back by a thick spacer .  That spacer acts as a dust shield and... well, I don't know what it's so thick.  But it does have a set screw and a Woodruff key, which will help me avoid cutting a keyway in the pulleys!  The idea was to bolt the pulleys to the spacer.  Here's the general arrangement, with the mill in the background.  Everything sort-of lines up.






Here's the key I was talking about.  But now that I'm writing it down, thinking about what others might advise, I'm not so sure this is a good idea... I'm thinking about how the pulleys could rotate relative to one another about clearance holes for machine screws.  Maybe I'll still do it but make a set of shoulder screws.  Or pins... 2 pins and a single machine screw.  And I can choose the order of the pulleys.  Probably would be best to counterbore the screws and that would be better in the large pulley. The small pulley, though, I may need to attach separately with smaller screws.  Maybe countersunk flat-head machine screws.  And pins.  Ug, so many decisions.  Or maybe I should cut a keyway and use the key at the other end of the spindle.  Anyway, this is what that keyway looks like.






I won't be able to get away without cutting keyways in the pulleys that go on the transmission shaft.  I found a few methods.  But a broach and press.  Buy a shaper.  Buy a slotting attachment for the mill.  But then I found this homemade lathe attachment.  These mechanisms basically mount on the cross slide and have a lever to manually cut the groove.










Here's a clever one that uses the compound as a shaper ram.  Again, it has a manual lever to advance the cutter.

http://madscientisthut.com/wordpres...haping-keyway-attachment-for-atlas-618-lathe/

Then I thought I might just mount the cutter in a tool holder and use a lever against the cross-bracing to advance the cross-slide with enough force to cut the groove.  The handwheel will spin wildly but I don't think it will be a hindrance.  The trick will be to keep the overhang of the slotting tool as minimal as possible.  And enough rake on the cutter that it's not trying to avoid the cut.  The pulley is "low carbon steel" which I think is cold rolled.  It machines OK.  McMaster says it's ASTM A108 which includes re-sulfered more machinable grads but also plain sticky carbon steels. So a little rake is probably OK.  And it can probably just be a HSS tool blank... Yeah, well, it sounds like good theory, right?

I also worked on the idler pulley.  It needs to be bored and recesses cut for bearings.  I think I've worked out a system for tensioning the belts with an over-center type linkage that is easily adjusted.


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## durableoreo (Aug 30, 2020)

I decided to try cutting the keyway using my lathe.  

About the cutter:  I started with 4 degrees of rake, based on a post on Practical Machinist.  The guy said: too little rake and the tool deflects out of the cut; too much rake and it digs in; no way to predict b/c depends on material, feed, etc but start at 4 degrees   I started with a piece of 5/8 HSS tool blank, which I blued and scratched out the width of the tool.  It is relieved in all directions so that only the front edge was in contact.  I did leave a small flat parallel to the cut to avoid the tool digging in.  Honed it was a diamond stone so it was really sharp and smooth.  I made sure to sharpen the front edge and sides as square as possible, making a perfect sharp corner.  I dabble in Japanese tools and the philosophy there is that the more perfect the edge, the stronger it is.  And Abom says you should hone the edge of HSS tools.  The width of the key was 0.4945 so I made my tool 0.4955.  I had to adjust that a bit at the end but I got as close as I could with my terrible grinder.

Here's a view of the side that runs in the groove.  The top edge is the main cutting edge.  The flat behind the cutting edge is about 2 times too big in this photo.  The relief behind the cutting edge is 0.010-0.020.






Here's the side view.  This is about 4 degrees.  Later I add a little more rake by tilting the tool in the holder.






Here's my setup.  It's janky but I did get it to work OK.  I drilled out the bulk of the material and cut at a rate of about 0.002 per 2 strokes.  There's something springy in the system so it would make a good cut and then another lighter cut.  The key is about 0.170" tall so it took quite a lot of elbow grease.  And every detail matters---oil, advancing the feed less where there was more material to remove, etc.  In the end, I noticed some dark marks in the way oil so I decided that this isn't the way to go.  Instead I'm doing the compound conversion from the previous post.  Basically, take the lead screw out of your compound and add a lever.  More on that next time. 

So to re-power the mill, I had to make pulleys.  To make the pulleys, I had to make a slotting attachment.  I think the better the machinist, the farther down the rabbit hole he can go.  Well, the best machinist already did a job like this and has the tool at hand.






View from the back






View from the front, watching a chip form.






And... success.  It's a good fit.


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## durableoreo (Sep 8, 2020)

I did some more work on the tensioner.  The handle might be a bit long but I'll try it as-is and make adjustments later.  The handle is 5/16 shafting and there's a 1-1/8" delrin ball on the end.






I've been piecing together the electrical for the mill.  I could throw it together with some wire nuts and electrical tape but I wanted to do it right.  So here's the progress so far.  There's an aluminum sheet with DIN rails for terminal blocks.  There's a power supply that puts out 12 VDC, and the VFD.  On the front panel there's a tachometer for the spindle, a voltage-amperage meter, an hours meter, switches for the lubrication pump and lights and DRO, and the panel for the VFD.  The start and e-stop are being shipped now.  Once those and the terminal connectors come, I can get started wiring it up.






How to situate the box is a bit of a problem.  I want it above the machine, above coolant.  Not too high, just where it's needed.  But the electrical box is big and it's not clear what should go where.  I think I'll put the electrical box above the back right corner.  The motor will stick out a bit on that side.  Then I'll attach the DRO on a swinging arm so that it swings in front of the hours meter but not the e-stop or VFD panel.

I'm changing my plan from screw-actuated axes to screw and lever feed.  Turns out, some of the fancier mills are set up that way.  So I'll leave the z-axis (y on a mill) with screw drive.  But for the x-axis I'll add an 80:1 gearbox and handwheel on the pinion.  I'll need a clutch, to disengage for lever use.  

And for the y-axis (the knee) I'll add a leadscrew.  Eventually.  For now, I'm just fixing the rack that was on it.  The pinion is fine but the rack was torn off the machine.  It was attached with some 10-24 socket-head cap screws, which were broken off flush.  Also, there were a pair of pins which measured 0.166" or so.  I ordered 0.175 drill rod, which is +/- 5 tenths.  I also ordered 0.1755 and 0.1760 reamers.  In my limited experience, a hole reamed to 5 tenths over the pin diameter gives a nice fit.  I'll drill out the pin holes in the rack on the drill press, bolt it into place, and use it as a drill guide for the hole in the mill.  Then I'll ream the holes in place.


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## durableoreo (Sep 11, 2020)

Finished the tensioning mechanism.  The casting is a bit rough but close enough.  The magic is in the offset shaft.  The offset is set using those 1/2" bars.  There's not a lot of room so I had to use some tricks.  Too much to explain, probably.  Anyway, the last steps are to add a stop to get the over-center effect and brace the other end of the shaft, and finish the idler pulley.  Then I can run the mill.  And I'll probably make T-nuts for my first project.  It's like the hello-world ritual of computer programmers or the champaign bottle of shipwrights.






The screws and pins came for the vertical rack.  Worked like a charm.  I re-assembled the knee and got the table back on it.  The motion is smooth.  Now I need to order gearboxes, if I've made my mind up.


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## durableoreo (Oct 15, 2020)

Had some more progress with the spindle drive.  I got all of the pulleys fixed on the appropriate shafts.  By hook or by crook.  I'm trying not to weld my way out of problems but I did stack the pulleys and weld them together---just a tack, actually.  I may eventually need to disassemble and weld more but until they break, I'll leave it.  It was touch-and-go.  I stacked the pulleys on the shaft, then made some tiny tacks (TIG, of course).  The first tack was just too much weld metal and it tipped the pulley enough to pinch the shaft.  Then I made a tack on the opposite side, hoping that the shrinkage would fix the problem.  It didn't help but I clamped the stack of pulleys during future welds, which prevented the warpage.  So the stack of pulleys on the transmission is sort-of permanently on the shaft but the other cluster slides on and off the shaft.






Still need to work out the drive side of the transmission.  I had originally designed the drive for a 3450 RPM but changed to a 3-phase 1750-RPM motor.  I think I will step the motor speed 2x at the input to the transmission.  Would be fine either way but this is the speed I designed around.  So... 2 more custom pulleys.  I want to buy but it's just not easily available.  A 2" pulley for 3L belts with a 3/4" shaft?  Can't find it anywhere.  If I had known, I would have designed around A belts (4L) for which there are many more options.  And for the motor, which has a 5/8 keyed shaft with a 3/16 key---no, McMaster only has it with a set screw. 

I fabricated a mount for the transmission.  It was a chore to get it mounted on the base.  I drilled the mount tap size (1/4-20) then tried to use a centering punch to mark the location.  Turns out, the cast iron, with it's chilly hard exterior, can't be easily marked with cheap punches from the usual suspects.  So i used a hand-held drill with the tap bit to mark the center of the first hole.  Then I drilled it with the clearance bit.  After installing a stud with appropriate jam nuts, I worked on the next hole.  All the while, the main casting of the mill is in the way.  And there's nothing to make you feel foolish like using a hand drill while you stand next to a drill press.










The input of the transmission is sort of a collet type arrangement.  Took a while to figure out how to secure an input shaft.  You're meant to put a collar over the collet.  There's even a hole for tightening the collar's screw.  (The collar is backwards at the moment so you can't tighten it properly.)










The tensioner pivot is finally installed.  It's close but not perfectly coaxial, despite making a tool to mark the center.  There are many places where I could have gone wrong.  But it's close enough to work---feels a bit sticky in one spot.  The final item for the tensioner is the locking mechanism.  The over-center idea just isn't going to work out.  Instead, I want to hijack the setscrew hole and use some kind of spring-loaded plunger to index the position of the tensioner.

The idler was originally designed with ball bearings and no provisions for positioning them on the shaft.  Not sure what I was thinking.  But the bearings were quite large and it made the pulley too wide.  So I switched to roller bearings and a set of thrust bearings on either side.  It's silly but appears to work.  






I finally got everything sort-of working.  I wired up the VFD and read through the 150 parameters to figure out which I needed to change.  Turns out, there were only a few that I couldn't use as-is. Here's a picture of the mill cutting into a bronze bar.  Turning that direction loosened the nut so I had to re-arrange, flip the cutter over, and mill from the other direction.  






At that time, I didn't have a key for the cutter so it was very light cuts for the first parts.  I managed to make a hybrid 0.050-0.250 key.














Then I started making T nuts---because that's what you do.  It's the equivalent of a "Hello, World" program for a horizontal mill.  I started with a chunk of mystery metal and it ended badly.  I noticed a lot of noise at the end of the first cut but carried on.  In the second cut, I could feel the cutting become difficult.  When I stopped to figure out what was going on, I noticed that the edge of the cutter was completely chowdered.  

Here's some stock preparation.  Looks bad but it's fairly smooth.  The gibs need tightening, looks like the arbor is wobbling a bit, and the operator needs experience!  Also, I won't be able to manage with this lever feed.






Now, cutting a shoulder, I hit some hard spots.  Checked with a file, too.










And here's what it did to the cutter


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## brino (Oct 15, 2020)

durableoreo said:


> Then I started making T nuts---because that's what you do. It's the equivalent of a "Hello, World" program for a horizontal mill.



Great line!
I like the way you think.
-brino


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## durableoreo (Dec 30, 2020)

Well, I finally got back to the mill last night.  Honestly, I thought this project would take less effort and that the results would be better.  In the back of my mind, I doubt that this will work out in the end, so I haven't been working on it for a few months.

Last night I managed 2 good cuts.  Turns out that the gibs weren't tight enough in the Y axis so when the cutter bit into the work, the X axis (traverses parallel to the cutter) would rock.  Belts were slipping, too.  So I tightened up the belt, locked the Y axis, and centered the vise over the knee.  The rocking is no longer visible.  Now it is apparent that lever feed is not going to work at all.  There is so much lash in my arm and the gears that I can't bring the work to bear solidly on the cutter.  I've heard people say good things about lever feed but was it roughing cuts in steel?  If you have used a lever-feed machine, please tell me about it.

If I can get 2 good T nuts made for the vise and machine down a brass nut for a 1/2-10 lead screw, I'll be a long way toward a power feed on X.

When I look back on the time and money, I might have been better off spending it on something I could convert to CNC.  Time is the only thing they're not making more of and I want to make better use of mine.  The clucking of the gray-bearded machinists might be right---not everything is better with a computer.  But still...  Well, I'm far enough in that I need to finish the project, so I will.


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## brino (Dec 31, 2020)

I am sorry this has not been going well.

Restoring an old machine is often a marathon of chasing one issue after another.

It sounds like you are making progress, albeit slower than you want and hard-won.

I still believe it will be a useful machine when you are done.

-brino


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## durableoreo (Mar 14, 2021)

After considering my situation and the weight and money involved, I decided I'd better finish the project.  Anyway, the problems I was having before are mainly due to an ad hock belt tensioner and lever feed.  Oh, and the paper towel I was using to protect the motor wasn't good for moral, either.  But all these problems can be solved.

Got some of the electrical details worked out.  The electrical box is mounted securely on an arm.  The DRO mounts on another arm but it's not installed yet.  I'm using Pheonix UT series terminal blocks to make the connections.  In an industrial application they use wire channels, too.  The machinist clamp and silly tape arrangement is critical because there's no hinge. 






There's an hours meter, spindle power consumption meter, the front panel for the motor controller, E-stop, and a start button.  I'm going to replace the start button with a selector type switch for Forward/Reverse.  Also need an On/Off selector switch.  I'm surprised at the difficulty in getting this wired up.  I'm an electrical engineer so I thought this would be fairly straightforward.  But the documentation for the V70 VFD (from stepperonline.com) isn't great, which results in several additional Digikey orders and a few more days wait.

There's a fan for cooling the VFD.  I want it to run when the spindle is turning.  The VFD has a relay which is perfect for this task.  I wanted a filter so I designed a plastic shroud for the back of the electrical box.  This is an example of using a 3D printer for something other than useless trinkets.  The resulting shroud is made of PLA and screwed onto the electrical box with coarse-thread sheet metal screws.  I decided to use a Honda cabin-air filter because it's cheap and available.






I got one of those cheap tachometers from eBay.  I think it's hall-effect technology and comes with a magnet but it looks a little like an inductive pickup.  The wiring diagram is wrong and in Chinese.  From watching YouTube videos, I was able to find how to hook it up.  Also, someone glued the magnet directly to a metal shaft and it worked.  The magnetic field changes dramatically when you stick a magnet to metal, so it was good to see it working.  I, on the other hand, plan to Renzetti the heck out of this.  I'm going to make a phenolic adapter between the flat magnet and the curve of the spindle.  More on that later.

Right now I'm trying to figure out how to mount the pickup.  There's a hole in the casting which was filled with cork.  It's only 0.590 in diameter and the sensor is 0.468.  I eventually decided on a flanged sleeve with internal threads.  The sensor is M12x1.0 which is not in my set of cheap taps so I ordered one from McMaster.  Near the flange there's a bit of a taper to keep the sensor seated.  If it vibrates out, I'll use a thixotropic compound that thins under constant shear.  I think that's how the Loctite thread lockers work.  Here's a drawing of what I'm planing.






I have most everything wired in.  I need some jumpers to short across terminal blocks, install the new switches, and wire in power for the DRO.  There's a lot of details in making it safe, dealing with multiple power supplies, and ensuring that the right things turn off when you press the E-stop.  You want the motor to stop but no need to turn off your work light and reset the DRO.  The choice of switches is important and expensive.  Some of these switches were 30 $ each.  But it's probably worth it.  Cheap switches will feel chunky and maybe not last very well.






A few things left to do:

1. Machine a nut and end plates for a lead screw that drives the X axis
2. Design a lead-screw drive for Z axis
3. Install power feed on the X axis

Then, there's tooling to figure out.  I have a single arbor and a bunch of spacers.  The arbor seems bent.  I wonder if the spacers' faces are parallel.  If not, they could be springing the shaft.  Below is a link to a video about that... it's toward the end.  I got out the surface plate and a cheap 5-10ths (0.0005) indicator to check parallelism.  For the thick spacers, 3 of the 4 were off by 0.001 which is enough to cause a problem.  That's measuring the highest spot on the line radiating from the center.  All of the spacers are crowned radially.  Also, I don't have precision ground stones so this isn't a reliable result.  (But I ordered some, about 165 $ on eBay.)  So I need to stone the surfaces, then re-measure, then do some lapping.  The fit is loose enough that 1-thou over or under won't cause it to bind against the shaft.











I may need to make another arbor.  Even if I can get by with this one, it's convenient to keep common setups on different arbors. 
Also, I might want to either find or make some collets.  But what is that taper?  And is the shaft round, parallel, and straight?  I got out the mystery V-blocks, checked them as best I could, balanced the arbor on it, and started measuring.  Couldn't make heads or tales of it.  It's round at the far end but the closer to the spindle nose, the worse it gets.  Seems like it's tapered by 7.5 tenths over 3.5".  So maybe that's OK.

The taper is about 40 degrees.  I measured it a few times and got 20.3 degrees.  Honestly, it's a project to measure it and this post is already too long.  But here's the setup and calculations.  Basically I lined up the V-block with the edge of the surface plate using a 1-2-3 block.  Then I used the indicator on the taper height and a caliper from the other edge of the surface plate.  I slid the arbor along until the indicator did a full turn and measured how far I slid it with the caliper.  The error on diameter is 0.62 degrees/thou and on the error on length is 0.2 degrees/thou.











Well, R8 collets are not in the cards.  Nor any other common sizes that I've heard of.  I guess I'll be learning to grind tapers here shortly


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## DiscoDan (Mar 14, 2021)

If you can give me a few measurements I will see if I can help identify the collet. In addition to the measurements in the picture, give me the threads per inch and the diameter of the widest part of the head (far right in the picture). Click on the picture to see the full picture.


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## durableoreo (Mar 14, 2021)

Thanks for the offer

A = 0.651
B = 0.635 (on the tips of the threads)
C = 2.210

Also, the largest part of taper on the arbor is 0.957.  The threads are 24 TPI.



Also, there is a keyway, about 0.100 wide.  And a flat for a 5/16 set screw in the nose of the spindle.  Judging from the damage pattern around the set screw, I'd say it is providing a significant amount of torque.  Or maybe it takes damage during a crash.  Here's a photo.


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## DiscoDan (Mar 14, 2021)

The closest collet I see is the 3PN from a P&W:

A=.650 body diameter
B=.645-24
C=2.063
Head diameter=.925 (I think)
3C and 1A have .650 diameter bodies but are longer, have 26 tpi and the other dimensions are off.

If the 3PN fit you could always make a new draw tube.


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## durableoreo (Mar 15, 2021)

DiscoDan got me thinking.  I stumbled on the ShopHardinge.com and happened on a catalog page that  lists just about every collet type I've ever heard of and a lot more. 



			https://www.shophardinge.com/categories.aspx?catid=126
		


If the link doesn't work, trim it back to the .com and follow the links to Top \ Workholding \ Other Lathe Collets \ Listed by Style

Seems like A1 might fit the bill.  Shank diameter is 0.650, threads are 0.640x26 and the length is 2.563".  There's no information about the taper but it probably is worth a try.  Also, 3C is very similar.










My collet doesn't match exactly---the drawbar is 24 TPI.  I measured it repeatedly using thread gauges and calipers.  In the second image, you can see that the threads are a little short of 24.  I measured with calipers and got an average reading of 23.43 thread/in.  So I think it's a home-brew arbor.  Those marks where the set screw bears---on a fractional horsepower machine---indicates that the material isn't very hard.  And the wrench flats, they're battered like a low-grade fastener.  And the flat that's ground on the shank, instead of the usual pin in the arbor, may also be a maintenance-shop fix. And look at the tapered part.  Isn't that fretting corrosion?  I'm guessing the arbor was made on a lathe with a slipping belt (or badly chosen gear train).  Now that I'm looking closely, the finish on the shaft looks like it's straight off the lathe, not ground.  And look at where the set screw falls---it is working against the drawbar.










Well, 3C collets have a half angle of 12 degrees.  So the DIY arbor has the wrong angle.  But what about the spindle?  Well, I measured it and it's about the same as I measured on the arbor, 20.4 degrees.  So the spindle may be home brew, too.  There's no way to put normal 3C collets in this spindle.  Instead of contacting the collet along the entire taper, it would make a circular contact, where forces would be very high, and there's no hope that the collet would function as it was intended.






An obvious solution would be mounting the lathe compound on the table and grinding the correct taper into the spindle.  Pro: an excuse to set up a tool post grinder.  Con: There's no way to avoid setting up a tool post grinder.  And the collet may sit too deep in the spindle.  I'll need to make a new drawbar with the right threads.

Maybe a better solution is to *make an adapter.*  Would it fall out each time I pull out a collet?  I can put a shoulder on it, groove the inside, and glue it into the spindle nose.  Some adhesive that is good in shear and compression, like a metal-filled epoxy.    Maybe I should groove the inside of the spindle, too. This will require internal-diameter grinding and lapping.  The lands of the adapter should bear directly on the spindle.

Another option would be to make a new spindle.  I don't think I could bore it through on my 9x20 lathe so I'd need to find DOM tubing and weld some flanges on.  And I'll finally be forced to cut threads for the bearing pre-load nut.  It's a big project.

I could also just make my own collets.  Problem with that is that Hardinge invented collets and settled on the dimensions that worked.  What's the chance that I'll have success after making a dramatic change?  From what I've seen on the eBay, 3C collets are going for 10--30 $ and I'd like to take advantage of what's already made.


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## durableoreo (Mar 15, 2021)

Thanks for the tip, DiscoDan.  Looks about right.  I don't know how you found that!






I started searching for 3PN collets.  I can't find anything on eBay.  The chatter on Practical Machinist is that they are rare and very limited in size range.  

I may need to switch over to 3C anyway.


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## DiscoDan (Mar 15, 2021)

That's odd, there is usually a ton of those 3PN collets on eBay. I usually just type in Pratt Whitney collet and they show up. Keep an eye out for them because there are usually a few on there. They are not as rare as the 4PN that I use in my P&W hhorizontalmill. But I did eventually find a set for mine but it took a while.


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## durableoreo (Mar 20, 2021)

I'll keep an eye out for the 3PN collets. 

I started poking around the web for 3PN stuff.  There's very little.  This taper is so rare that it mainly lead to the few other who have the same milling machine.  Apparently it is a Jefferson horizontal mill.  It has been sold by dealers under Delta and re-badged as a Carroll.  Carroll was mainly known for lathes   Other users who have the same mill:

ThunderDog, 2014, https://www.hobby-machinist.com/members/thunderdog.35578/
Tew45, 2013, https://www.hobby-machinist.com/members/tew45.45873/
Mark_w, 2017, https://www.hobby-machinist.com/members/mark_w.47851/
If I want to use 3C collets, I need a flanged adapter to convert the spindle's taper from 20 degrees to 12 degrees.  Sketch below.  Shouldn't be too difficult.  There's some cylindrical grinding involved but nothing too crazy.  I ordered a 500-W Chinesium spindle cartridge with speed controller and mounting hardware.  I may be able to adapt that to my lathe tool post without too much trouble.  I was thinking O-1 for the adapter but then I remembered that it's not the easiest to machine, despite my familiarity with heat treating it.  Seems like it should be fairly hard because the forces from the collet closer all bear on that surface.  Any  ideas for materials? 






I started looking arbors.  On eBay, the only 3C offering has a 1/4" shaft and costs 100 $.  I want to use cutters that mount on a 1-1/4" arbor.  I don't see any way to avoid making a new arbor.  That's not an emergency, though.  Maybe I should finish the electrical panel first.

Thinking about 3C collets, I also have a 9x20 lathe which has a 3/4" spindle bore.  Looking at the chart, the only C series collets that will fit is #3.  So there's some economy in using the same collets on both machines. To be fair, it's the imaginary kind economy where you spend a money and console yourself with the idea that you could have spent more.  

About the electrical panel, it's finally finished.  I was waiting for the right switches to arrive and for jumpers that short terminal blocks together.  It looks a little messy but everything works.  There's power for the DRO, a work light, tach, power meter, hours meter, on/off, direction, and E-stop.  I thought I had chosen all the meters to be the same color but it looks like I have 1 of each.  






I closed up the box, a momentous occasion, and put the mill back in the corner.  It has been in my way for months because I needed access to the rear for the re-powering part of the project.  I tried out the tachometer.  I literally stuck the magnet on the spindle shaft and it worked.  Probably not recommended for all cases but at 50 RPM, it's probably OK.  I should probably put a little CA glue on it, just to be safe.






Getting the tachometer sensor installed took longer than expected.  First, I had to wait a few days for a M12x1.0 tap.  The hole in the casting was
machined flat on the outside but inside was curved so it was difficult to get everything installed.  Also the spindle was in the way.  But it all came together eventually. 






I started looking at the DRO scales, wondering where to put them.  On a small mill, there's no good place for them.  I took one of the scales apart, trying to figure out if anything could be made smaller or if the chunky case could be modified or discarded.  No inspiration struck so I re-assembled the scale and put it back in the box.  This kind of stalling won't work for long---only until I have the lead screws installed for X and Z,


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## durableoreo (Mar 21, 2021)

I abandoned the T-nuts for now.  To convert the x-axis from lever to 1/2-10 leadscrew, I need a nut that is about 3/4 high.  Here's a little progress on flattening a 1-1/2 brass nut.  I've had trouble with lever feed so I tried setting the depth of cut and using the screw-driven y-axis too sweep across the part.  Works fine, which gives me hope for this project.  But it's also nonsense.  So I took up the lever and tried cutting half the cutter width---maybe 3/16.  On first approach, it's rough and I can hear vibrations.  Some teeth are cutting more than others.  I thought there was runout in the shaft but careful measurements did not confirm.  Maybe the cutter is badly sharpened..  or the taper in the spindle is off.  Or it could be operator error.  Anyway, after the cut progresses 1/2" into the work, everything sounds and feels better.






Probably should have used my dry-cut saw to rough this in...






The spindle for my ad hoc grinder came today.  The abrasive wheels also arrived.

I ordered a universal single-lip grinder, a.k.a. d-bit grinder.  I've been agonizing about this for a while.  It's quite a bit of money and I have no proof that it will give me a good return on the investment.  I need a way to sharpen cutters.  They're fairly cheap online but many used.  Some have sloshed around in a box for years.  It is easy to damage a cutter, especially the small ones.  I have found no information about grinding milling cutters on a d-bit grinder but I think it can be done.  I think the trick is to mount an adaptor in the collet that coverts from 1/2" shank to the arbor diameter.  It's hard to visualize and I'm not sure it will work.  It's also possible I will need to make a custom holder.  More on that later


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## durableoreo (Mar 22, 2021)

I started milling the nut for the x-axis.  I had a 1/2-10 acme nut from another project.  The space under the milling table is 3/4" high and 1" wide.  So I cut the nut down to a little under 3/4. I was a relief to be able to complete a simple task like this without a hacksaw or file.  I hope those days are behind me.  

I touched up the cutter with a segmented diamond plate.  I think it's normally sold for sharpening knives.  But for brass you want really sharp cutting edges.  The finish was good.  I had to take narrow cuts, 1/8--3/16, or else the belts would slip.  It's a 4" cutter and I  was running the mill at 75 RPM, which is fairly speedy.  






Action shot.  Note the piece of shaft acting as an impromptu parallel.  The vice seems to lift the part so I had to hammer it down onto the parallel.  The ends of the nut aren't parallel enough so I am using a strategically placed piece of 14-AWG copper wire.  The vice is only held onto the milling table with a single T-nut and the gear driving the x-axis had a loose tapered pin so there was a lot of slop in the system.  Better every time but it's still marginal.






Here is the partially finished product.  I need to cut the other dimension to 1", then drill holes where the nut will be mounted to the saddle (the y-axis casting).






I unpacked the chinesium power feed.  It's huge.  I'm not going to be able to use it.  So I got on eBay and bought a NEMA 23 stepper motor with right-angle 1:17 gear box, driver, DC power supply, and pulse generator.  For 1 IPM feed through a 10-turn lead screw, it will 170 RPM on the motor.  Stepper motors have fairly high torque at low-ish speeds so this has a chance of working.  If not, I'll add a 2:1 gear box.


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## durableoreo (Mar 22, 2021)

Finished the lead screw nut for the long axis of the table.  I didn't spend a lot of time checking dimensions.  The vise isn't trammed and there's literally nothing I trust about the mill.  Also, I was in too big a hurry and didn't even check to see how far out it might be.  Not all the dimensions are critical but keeping the lead screw parallel to the table is important.  Unfortunately, there is about 0.008 variation from one end of the nut to the other.  In this case, I may be able to get away with some shims.  A proper machinist would be to fix the problem and correct the part.  But I don't know how to fix the problem without buying another vise.  And maybe there's still other problems that I can't see until the vise is fixed... 






Have a look at the finish.  The larger scallops are at the beginning of the cut.






I am taking fairly deep cuts, around 1/4" but only 1/2 the width of the cutter, maybe 3/16".  There's runout somewhere in the system so one side of the cutter, perhaps only a few teeth, are taking a larger cut.  When I approach the work, the cut is quite rough.  The sound and feel are a little alarming.  You can see it in the finish.  When the cut is deep enough that 2 teeth are in the work, everything sounds better and the finish is better. 

One of my previous obsessions was hand saws for wood working.  In the English tradition, one chooses the saw that has about 3 teeth in the cut.  Usually you cut at an angle so it's not as simple as knowing the thickness of the stock you're cutting.  In that case the additional teeth set the toll pressure.  The chip load can be a big problem with wood so more smaller teeth is counterproductive.  The Japanese tradition goes by the length of the saw, which is closely tied to the number of teeth.  The teeth have a completely different geometry but it's all the same in the end---too many or too few teeth in the cut is a problem.

I think the sound and vibration is coming from the lever/pinion/rack that drive the long axis of the table.  I can see it clattering even as I try to hold it steady.  It is worse when a single tooth is in the cut. If the lash in the rack-and-pinion is causing the problem, I hope that the lead-screw feed will solve the problem.

This is where the nut goes.  The channel that the teeth of the rack occupy is 1" wide.  I will need to file off the corners to get the nut fit, then bolt it into the saddle.  Once that point is established, I feel like I can easily make end plates for the table that accommodate the screw, wherever it falls.






Visual check of the height of the nut.  I might need to take a little more off.  The rack is 3/4" but I forgot about the recess it sits in.






In brass, the cutter definitely cuts better when it's razor sharp.  Keeping it so is difficult.  Using a stone, hand-held, is difficult but does work.  I'm looking forward to using the d-bit grinder to sharpen cutters.  I've not seen it done but I read a post somewhere (here or practical machinist) about how to do it.  I also ordered the endmill sharpener, which allows the cutter to turn in a helical path.  This would be mainly for sharpening slab cutters.  At least, that's what I was thinking a week ago.  But from my recent experience, I am no longer sure if the mill is capable of running a 1" wide slab cutter.  It stalls easier than I expected---the spindle, not the motor or 15:1 transmission.  So I might need to re-visit belt tension, make better pulleys, or convert to a cog or multi-V belt type drive train.

About grinding cutters, I've been assembling a list of possible uses for a universal d-bit type machine.  There's probably lots of other tasks that I just don't know about.

Sharpen milling cutters
Sharpen slitting saws
Make d-bit endmills (all 8 types)
Make d-bit reamers
Make dovetail cutters
Sharpen endmills (ends yes, flutes maybe)
Sharpen drills
Make carbide spade bits
Make counterbore bits from twist drills
Grind tapers
Relieve end mills for longer reach
Grind lathe tools


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## ericc (Mar 23, 2021)

I'm suspicious that something else is wrong with the x axis feed.  Lever and hand wheel feeds have been used successfully for decades on production horizontal mills, and not just for cutting soft metals.  Is there a lot of backlash in the axis?  If you try to wobble it by hand, is there obvious movement?  Internet wisdom says that backlash doesn't matter, but it really does if it is severe.  Before expending a lot of effort on a lead screw conversion, I'd be tempted to try to cobble together some kind of temporary screw feed to test what is going on.  A large C-clamp can be the start of such a test.


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## durableoreo (Mar 24, 2021)

ericc said:


> I'm suspicious that something else is wrong with the x axis feed.  Lever and hand wheel feeds have been used successfully for decades on production horizontal mills, and not just for cutting soft metals.  Is there a lot of backlash in the axis?  If you try to wobble it by hand, is there obvious movement?  Internet wisdom says that backlash doesn't matter, but it really does if it is severe.  Before expending a lot of effort on a lead screw conversion, I'd be tempted to try to cobble together some kind of temporary screw feed to test what is going on.  A large C-clamp can be the start of such a test.



Good question.  Let me check...

When I received the mill, I took apart the x-axis and cleaned it completely. I re-assembled and lubricated with way oil.  The gib is tightened down as much as possible.  There is a bit of stick-slip when I pull on the lever so it may be slightly tighter than necessary.  

The pinion gear is held onto its shaft with a tapered pin, which was not driven home.  That resulted in lash between the lever and the pinion.  I've fixed that and it helped a lot.  There is some lash in the rack/pinion.  I just measured it now.  I was going to measure lash of the table but it's really hard to move by hand.  I put the indicator on the pinion and measured about 0.010" of total movement.







When I'm cutting, there is perceptible motion in the table but it's hard to figure out where it's coming from.  The x-axis is tightened to the point that an 1/8 turn more on the gib-adjustment screws is a problem.  The y-axis is similarly tight.  And the z-axis, which both x and y are on, is locked tight.  Still, if I put a good test indicator on the table, I can deflect the needle 2-3 thousandths in either direction with 50-80 lb of pressure on the table.  If I press in the middle of the table, the deflection is closer to 0.001".  Seems fairly squishy.

After reading you comment, I finished the T-nuts.  Felt similar to machining brass, actually.  I was as likely to jam the cutter and slip the belts with both materials.  After tightening down the vise properly, there was no difference---still super twichy and difficult to feed without jamming.  I tried a smaller cutter with more teeth, which also didn't help.






THEN, I measured the spindle runout.  The spindle is running out 4--5 thou.  This explains the trouble feeding, I think.  It explains the pulsing I feel in the lever.  And combined with the stick-slip of the x-axis, the feed is probably jerking, causing the cutter to bite too hard and slip the belts.  From Machinery's Handbook, a few thou cut per tooth is a typical feed rate.  So if I'm trying to feed normally on the low side of the cutter, when the high side of the cutter comes around, it's trying to take a huge bite.  I noticed that I sometimes would get into a rhythm, advancing after the high side took a cut and slacking off a little when the high side came around again.  It's 70 RPM and you can hear and feel that something is out of round.

I've already check the arbor.  The arbor seems perfect, on the surface plate.  BUT the spindle is a train wreck.  I'm getting 0.004" runout wherever I measure---in the bore, on the spindle nose, on the taper.  I removed overarm, nut, and spacers, which made no difference.  I tightened and loosened the bearing pre-load but nothing changed, whatever the setting.  I measured with very light belt pressure and heavy belt pressure---maybe 0.0005 variation in runout.  I measured the diameter of the spindle nose with a micrometer and got the same readings all around, within a few tenths.  Is there an other explanation other than a bad bearing?  Seems odd that the runout is bad at both ends of the spindle.  

I pulled the spindle and bearings.  Both inner races are too loose and are rubbing on the spindle.  There are burnished lines on all of the rollers which, in my imagination, indicates a metal chip getting jammed between a roller and a race.  Probably it was a metal that was softer than the bearing components.  Abrasive wear looks different---more of a cloudy effect.  See the p. 47, Figure 10 in the SKF failures-analysis publication.  Abrasives, if I understand it, are very hard but mostly brittle.  They don't burnish but catch on the roller, pulling the article under the contact patch.  The abrasive particle then breaks, making even smaller abrasive particles.  But I have distinct shiny rings on my rollers, not hazy tumbling abrasive patterns.

I ordered new bearings, just in case.  Not sure if that will fix the problem. 



			https://www.skf.com/binaries/pub12/Images/0901d1968064c148-Bearing-failures---14219_2-EN_tcm_12-297619.pdf
		












I read some more about TIR and I can't see how the bearing could be causing consistent deflection at low-speed (30 RPM).  So I measured the shaft.  Where the front bearing touches the spindle shaft, near the nose, the spindle is out of round.  To avoid errors from the spindle is mounted, I measured it with v-blocks (wide and narrow sides) and suspended on a rod between v-blocks.  All measurements gave the same result---about 0.003 deviation from one side of the shaft to the other.  The other end is better.  These measurement correspond to the scuffing on the inner races, too.






So now what?  Shim the bearing?  Make a new spindle?  I'm not super confident about turning a new spindle.  Haven't turned between centers before and my first single-point threading on the 9x20 was a disaster.  It's a long bore, far longer than I've ever done.  It would be an opportunity to change the collets... Maybe instead I could true the shaft on the lathe, make a bushing, split it, and press the bearing over the bushing.


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## ericc (Mar 24, 2021)

Good investigation.  That's an interesting question about the spindle.  I'll see how much my table shakes.  I think it is very little.  My little horizontal mill does shake and buck if the gibs are not well snugged, though, especially when cutting with a flycutter.


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## ericc (Mar 24, 2021)

I just checked.  The x-axis is 13 thou, even with the gibs snugged.  The z is even worse, with side to side shake.  I have to make sure to snug everything before a heavy cut in steel.  But it does work.  The x movement is due to screw backlash. Part of normal operation.  I think the arbor also has significant runout, but with a flycutter, it's fine.


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## durableoreo (Mar 24, 2021)

I'm considering my options for the spindle repair.  I thought I might get a similar bearing with a larger bore.  That would give me some leeway to repair the shaft.  I downloaded the Timken catalog and found the catalog numbers - 1985 for the inner race (with rollers and cage) and 1931 for the outer race.  The nominal shaft diameter is 1-1/8 (1.125") and the bearing OD is 2-3/8 (2.375").  I searched for all bearings with the same outer race and found that 1.125 is the largest shaft supported.  I also dug through the other types of bearings, just to see if any other bearing could be pressed into the housing.  I found nothing. I went through the catalog, using the PDF search function.  I used cad.timken.com to do parametric searches of the available offerings but found nothing.  After looking, I realized that the repair to the shaft is the key and that any solution can accommodate the original bearing.  So it was an educational dead end.

Is it practical to turn down the shaft (where the inner race sits) by 0.003--0.004 and replace the lost material with a ring of brass shim stock?  If I remove little, the shims would be thin and fragile when pressing on the bearing.  If I remove too much, the strength of the spindle will be compromised.  An intermediate solution lends itself to cutting a precise collar on the lathe, which could then be chamfered to ease the bearing on and split (halves) to get it onto the shaft.  Maybe a band clamp would be needed to keep everything in place while pressing the bearing on half way.  I suppose there's no reason to use a soft metal, either.  I am thinking some half-hard O-1 might be a good place to start.


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## durableoreo (Mar 26, 2021)

I decided to turn down the shaft and fit it with a precision split collar.

Turning between centers is probably the way to go.  I don't have a center for the spindle nose, so I tried mounting the spindle in the 3-jaw chuck.  It was running out 0.005 so I fiddled around with shims and tapping various jaws for a while.  It was within 5 10ths eventually but after taking a few light cuts, I measured a variation of 0.002. 






It's fairly round---1.1049 one way and 1.1050 the other way.  I tried measuring the runout of my cut in several ways.  First, I used precision ground stones to clean up the surface.  Then I rolled it on the surface plate, with the nose hanging off.  Not sure if I was getting accurate results, I also tried on a v-block and in a vertical mode.  All resulted in the same measurement, about 0.002 variation in the area I cut.  This is measuring the same points on the shaft each time.






The vertical measurement is a little strange.  I'm waiting on a snug so I can do a better job measuring vertical deviation.  You can see the stand and ball bearing in the background.  There are lots of assumptions with this measurement.  For example, is the nose perpendicular to the shaft?  Is the nose round?  Turns out, it is fairly round, measuring 1.4349 and 1.4350.  There were parts that could move relative to each other, non-machined services, etc.  Anyway, if it didn't give me results consistent with my other measurements, I wouldn't believe any of those numbers

Well, my efforts to shim (and tap) the chuck were not successful.  I think I'll need to make a large center with a drive screw.  If I make it on my lathe and don't take it out of the chuck, it will be a minimum runout situation.  Also, it will be a chance to check the alignment of the tailstock, another critical aspect of getting a good result.

An O-1 blank is on the way from McMaster so I can start working on the collar soon.  I think I'll be grinding the inside and outside on the lathe.  So I need to build a mount for the grinder...


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## durableoreo (Mar 28, 2021)

I was watching Suburban Tool videos (as one does) and happened on a spindle-repair video (around 14:00).  They've mounted a spindle using spiders, which they call "caps".  They're using it for rough OD grinding. 

Also, they measured spindles on v-blocks with a height gauge, one of the things I tried.  Their v-blocks probably matched and were not purchased from Amazon.  Or Shars. 






The idea of making a cap is more appealing than making a dead center and a lathe dog.  So I dug out a 2" round of 1215 and made a cap.  The hole is about 1.5" and the screws are hardware-store grade 10-32 with jam nuts. It was a challenge to get everything running true.  It's pretty crude compared to a proper 4-jaw chuck.  Before my 3rd cut, I added brass plugs under the screws, which was a huge improvement.






For the 2nd cut, I took the lightest possible cut to clean up the shaft.  I used a home-made HSS cutter that was honed to a razor's edge.  After taking 2 very light cuts, I took it back to the surface plate.  The measurements were difficult.  After taking a set of measurements, I went over the surface with 800-grit sandpaper, which improved repeatability.  Then I took another set of measurements. The measured runout was 0.002 before the 2nd cut and 0.001 after.  Better but I'd like to get it down below 5 10ths.






I needed to improve the spider a bit and make another cut.  When I tighten the screws, it rotates the work.  And maybe there are other problems, hidden by my inexperience.  I added brass plugs under the screws, which is a bearing material.  I switched tools and ran it over the diamond stone, dressing the edge and radius.  I thought I might set the gearbox for a slower feed but I ended up hand feeding.  I snugged up the gibs and adjusted the tool height before making the cut.

After the 3rd cut, I took another set of measurements.  I'm measuring every 90 degrees and at 4 places along the cut.  First few measurements were good then got worse.  I had added a v-block clamp and it may have been raising burrs on the shaft. Runout got worse.  Then I stoned the shaft carefully and used a wood block to protect the shaft.  The runout was comparable to the measurements before I added the clamp,  Looks like I've gotten runout around 0.0005, which was my goal.  I think I'd need to set up an OD-grinding fixture to do better on my equipment.











Here's the final measuring setup.  Had to use a single v-block because none of mine match.  It wasn't balanced so I had to press it down while measuring.  The wood block protects the shaft and the gauge blocks are there for sanity.  When things are weird, it's a psychological relief to be able to check your indicator.  This is the BesTest and it's better than the cheap meters.  But having taken several hundred measurements tonight, I see that it is not perfect and also that my stand is just not adequate for 50-millionths measurements.  Every time I bump the indicator, it's got to be checked.  Even approaching the work rapidly can mess it up.  Approaching the work by pushing or pulling gives different results.  A certain amount of tapping was needed.  Several times I thought something was wrong but the indicator settled into the expected answer after minutes.  Maybe i just turned away and the vibrations from the house helped the meter overcome internal stick-slip.  Whatever it is, these measurements are harder than I expected.  I think the last set of measurements took me 4 hours






I took some measurements on the live center in the tailstock.  Runout wasn't great.  Maybe I should flip the part around to cut a groove for the rear bearing repair.  Near the chuck, it's easier to adjust. 

Thinking about the sleeves I need to make for this repair---they will be challenging pieces.  I want to cut the OD to size and trepan instead of the usual drill & boring bar routine.  But the dimensions are so critical and I'm not sure I can deal with adjusting the ID after cutting that part off.  Can't measure it accurately until it's off.  I might be better off boring out the center because then I can use telescoping gauges and mics.  Adjusting dimensions seems easy while the sleeve is attached to the stock.  Still thinking about how to do that.  And how to split them... They'll only be 1/16" thick and 3/4" wide.


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## durableoreo (Jul 16, 2021)

I've machined the spindle OD down by 0.020.  I'm going to try to press the bearing over a piece of shim stock ALTHOUGH it is a ridiculous plan. I've slept on it a few nights...  Still, I've already put some work into it and it's inexpensive.  Well, I bought a Palmgren 2-ton arbor press so I guess it's not as inexpensive as I expected.  But a man needs a press.  I've needed this for 15 years.

I thought about getting a new spindle machined.  I might need to make a new arbor, to match.  But I'm going to try the shim method first.


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## durableoreo (Aug 20, 2021)

One quote for a new spindle was 600 $, the other was 750 $.  

On the path to 3C collets, I need a pin to prevent the collet from rotating.  There was a 5/16-18 hole in the spindle---perfect.  So I purchased "alloy" dog-point set screws from McMaster and used the D-bit grinder to turn the point down.  It was fairly hard material.  Nice orange sparks.  This is the first job I did with that D-bit grinder.  The arbor isn't tapered so it's main use is a 320-grid diamond face wheel.  




To hold the screw, I made an aluminum adapter, turned to 0.501 on the OD and threaded it for 5/16-18.  The first screw protrudes and the one behind it jams everything securely. Unfortunately, it's not a machinist fit on the threads (maybe it's my cheap taps) so the tip didn't quite grind symmetrically.  Very close.  Close enough for this job.





The set screw is glued in with medium Loc Tite 242.  I wanted the head of the screw flush for safety reasons and vanity.  To get it all to fit, I ground the tip shorter.


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## durableoreo (Aug 22, 2021)

Well, I'm back to thinking about how to adapt the 3PN spindle to 3C.  I was originally going to make an adapter (as one does) but I'm not 100% confident that I can do it.  

Another option is using a MT3 -> 3C adapter.  The MT3 end is larger than the current taper.  If I start with this part, I can skip a lot of the work.  But will it be too hard to machine on the OD?  If it's hard, all I have is some brazed carbide tooling---no CBN.  It would be too much material to remove with a makeshift toolpost grinder.






Here are a few possible adapters.  The first is... low profile.  Difficult to make.  The second design, with the flange, is probably more realistic.
I'll print them in PLA first and then see about making one in O-1. I'm thinking mill within a few thousandths, harden, and then grind the OD on a 3C-tapered arbor in the lathe.  Then glue the adapter into the mill's spindle and grind the ID _in situ.  _Will need to mount the mini lathe compound on the table... 

I had previously purchased some parts to make a tool-post grinder.  But I ended up buying the Black Eagle Precision unit on eBay.  Mounts right up to the AXA tool post.  A proper hobby machinist should drop everything and spend 6 months building an awesome grinder.  I don't have a working mill so I thought I should just buy the grinder and get on with it.


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## Firstram (Aug 22, 2021)

What an adventure, keep your positive attitude and you will get there.


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## durableoreo (Aug 23, 2021)

Firstram, thanks for stopping by.  Southport... I've been down that way a few times.  You're near my favorite donut shop---Wake and Bake, in Carolina Beach.

Back to the irregularly scheduled show... I made some taper adapters on the 3d-McPrinter.  The gray-haired machists don't even bother to cluck at this contrivance.  But I'm not a real machinist so it's allowed.  Turns out that the printer struggles with a fine taper.  It like a low-resolution monitor or an apprentice coil-pot maker.  The trouble is the plastic-extruder nozzle diameter.  It produces a bead of plastic that is 16 thou in diameter which is a giant step-over in an application like this.  Normally a small step-over can be used but the taper is on both sides and the distance from one wall to another is small.  A thick part would be able to take up the difference between the outer shells.






Just to get an idea of the bearing, I marked up the collet and spindle.  The bearing is 100% on the discontinuity discussed above.
Did the same procedure for the low-profile collet.  Similar issues.  Also, plastics can grow or shrink a bit.  There's a scaling factor in the software. When I was making a grease seal for the spindle nose (a future post) I had to correct for shrinkage of 2.4% when printing with PolyFlex TPU95.  I didn't make any adjustments for these parts because these are simply visualization aids and not real parts. 

I probably will try the plastic adapters in the mill.  I had an amazing experience with 1-1/2" dimple dies in a 20-ga stainless pan.  The dies were 3D printed PLA.  These are ABS, which is actually not as good as PLA in compression.  I think PLA has E = 350 ksi and ABS is half of that.  Steel has E =  31,000 ksi.  Silly thought it may be, I'm curious how well it will work.  There's a video of a kid who made a weird Morse taper collet out of PLA and ran a fly cutter in it. Watch and cringe.








Still thinking about how to machine the ID of the adapter in steel.  The OD might not be so bad.  But if the outside is tapered, there's only a thin flange to hold onto...


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## ericc (Aug 23, 2021)

>I probably will try the plastic adapters in the mill.  I had an amazing experience with 1-1/2" dimple dies in a 20-ga stainless pan.  The dies were 3D >printed PLA.  These are ABS, which is actually not as good as PLA in compression.  I think PLA has E = 350 ksi and ABS is half of that.  Steel >has E =  31,000 ksi.  Silly thought it may be, I'm curious how well it will work.  There's a video of a kid who made a weird Morse taper collet out of >PLA and ran a fly cutter in it. Watch and cringe.

31000 ksi is a pretty strong steel.  And those are strange units.  I had to look it up.


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## Firstram (Aug 23, 2021)

You could bore an internal taper as close as you can, than turn the external taper to match the spindle. Part the adapter off, locktite in place and grind the ID in situ.


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## Weldingrod1 (Aug 23, 2021)

I'd use the flange style. The double taper will want to move back and forth in use, breaking the loctite.

Sent from my SM-G892A using Tapatalk


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## durableoreo (Aug 23, 2021)

ericc said:


> >I probably will try the plastic adapters in the mill.  I had an amazing experience with 1-1/2" dimple dies in a 20-ga stainless pan.  The dies were 3D >printed PLA.  These are ABS, which is actually not as good as PLA in compression.  I think PLA has E = 350 ksi and ABS is half of that.  Steel >has E =  31,000 ksi.  Silly thought it may be, I'm curious how well it will work.  There's a video of a kid who made a weird Morse taper collet out of >PLA and ran a fly cutter in it. Watch and cringe.
> 
> 31000 ksi is a pretty strong steel.  And those are strange units.  I had to look it up.



Hmm.. I admit I'm out of my league on material properties.  I have seen ksi (1000 lb per square inch) in some of the J F Lincoln books and around the web.  It is often in tables of material properties, which is why I used it.  I'm not religious about it, though, so I'll add GPa for the metric minds out there.

Looking more carefully, I'm seeing 200 GPa (30 ksi) for steel.  I found a paper [1] that says that PLA has a Youngs modulus of 3.5 GPa (507 ksi). Those measurements are for tensile stress.  

For ultimate strength, mild steel is about the same in tension and compression, so around 200 GPa (30000 ksi).  PLA, on the other hand, is much stronger in compression.  This study found that PLA failed in compression around 50 GPa (7251 ksi).  That's 4 times weaker than steel but it's so damn easy that it's hard to resist.  Also, compared to the strength of aluminum, PLA is not bad.  Now-a-days there are companies that produce press-brake tooling from PLA, which I take as social proof of the material's suitability for this weird application.  It's worth a try, at least.

1. http://2015.igem.org/wiki/images/2/24/CamJIC-Specs-Strength.pdf


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## ericc (Aug 23, 2021)

durableoreo said:


> ...
> 
> Looking more carefully, I'm seeing 200 GPa (30 ksi) for steel.  I found a paper [1] that says that PLA has a Youngs modulus of 3.5 GPa (507 ksi). Those measurements are for tensile stress.


This comparison doesn't look quite right.  It is saying that PLA is almost 6 times stronger than steel.  Could these be switched around?  Also, are you sure the first units are GPa?  It seems that MPa would be more reasonable.


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## Firstram (Aug 23, 2021)

Weldingrod1 said:


> I'd use the flange style. The double taper will want to move back and forth in use, breaking the loctite.
> 
> Sent from my SM-G892A using Tapatalk


Once the ID is machined the loctite wouldn't be needed.


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## durableoreo (Aug 23, 2021)

ericc said:


> This comparison doesn't look quite right.  It is saying that PLA is almost 6 times stronger than steel.  Could these be switched around?  Also, are you sure the first units are GPa?  It seems that MPa would be more reasonable.



I may not have explained it well.  But for clarity, here's a list of E values [1].  The list makes it easy to compare values for ABS, A36 steel, and aluminum.  PLA isn't listed but the other study [2] had a reasonable value for E in tension.  The most important thing is that  showed the compressive strength of PLA, though.  

As I was thinking about your comment, I saw that carbon-fiber filled plastic is also on the list.  It has E = 150 GPa (21,755 ksi) which is A-MA-ZING.  I have carbon-fiber ABS and carbon fiber-nylon filament on the shelf, ready for a project like this.  So I'm glad we had this conversation!

Anyway, I don't want to over emphasize this whim/lark/fancy.  I'll try the plastic collet adapter and let you know how it performs.  But first, I've got the rest of the mill to fix.

1. https://www.engineeringtoolbox.com/young-modulus-d_417.html
2. http://2015.igem.org/wiki/images/2/24/CamJIC-Specs-Strength.pdf


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## Weldingrod1 (Aug 28, 2021)

CF ABS is much easier to print. CF nylon really wants garolite and glue, or maybe glass and glue.

I'm deep the the glass fiber nylon rabbit hole right now ;-)
	

	
	
		
		

		
			





Sent from my SM-G892A using Tapatalk


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## durableoreo (Aug 29, 2021)

Weldingrod1 said:


> CF ABS is much easier to print. CF nylon really wants garolite and glue, or maybe glass and glue.
> 
> I'm deep the the glass fiber nylon rabbit hole right now ;-)
> 
> Sent from my SM-G892A using Tapatalk



That is a nice looking part. Post a link if you've got a thread going!

I've had good luck with ABS.  It will curl up on the corners a bit but a brim seems to solve the problem.  I have nylon too but haven't gotten to it yet.  Need to install the hardened nozzle and give it a try.


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## durableoreo (Aug 29, 2021)

Started on the adapter.  I don't know what's taking me so long.  A bunch of new operations, maybe, lots of unknowns.  Anyway, here's the plan:

Center drill, step up to 0.250, 0.400, 0.500, then bore to 0.650
Dust off compound, set to 12 degrees, and bore ID that will accept 3C collets
Set compound to 20 degrees (to match spindle) and machine OD
Turn flange
Part off
Heat treat O-1 and draw to R_C 58  (click here for history and details of the alloy)
Make a split-ring collar to set the depth in the chuck, holding the part by the flange
Grind the OD (check with hi-spot in spindle)
Install the adapter in the spindle with a tiny amount of Loctite 609 under flange and clamp with the draw bar
Grind ID in-place
The chicken scratching below didn't scan very well but it'll give you the general idea.  So far, I've only done step 1.  I did manage to find my compound, too.




Setting the angle on the compound accurately is my next problem.  I decided to do the trig method where you measure the legs of a triangle.  The ways are 1 leg and the other leg is perpendicular.  I'll move the carriage x along the ways and adjust the compound until the tool post moves by the right amount in y.  The tool post will be square to the chuck for this operation.  Whatever I use for x, y = x * tan(angle).  Tangent isn't too crazy for small angles so I hope this works.  Other methods might be more accurate.  If I don't get a good print, I may need to use a different method.

For now, I need some carriage stops to control the length of the x leg and I'll use an indicator against the took post to measure the other leg.  I was going to buy a carriage stop but one of the first things I saw was this 3-d printed thing and he wanted 45 $ for it.  Seems like a lot.  Also, this is one of those basic projects that you're meant to do for yourself.  So I decided to make a pair.






It's un-filled ABS with a 3/8 hole for drill rod or an indicator and a 1/4-20 clamp for the dovetail.  The hinge is integrated into the body.  It's 50% filled, which is fairly stout.  I bought knobs from McMaster and some "press-fit" threaded inserts. After shipping and the extra parts, it was 42 $ for 2 stops.  

BTW, I'm not a fan of the 3-d printing hype and various trinket printing that goes on.  If I had a working mill, I would make this out of brass or aluminum and feel smug about it.  But for now, the plastic version will have to do.  I do not intend to over use the FDM printer (partly due to all the clucking) but I've been surprised at where it can be used effectively.  I'm keeping an open mind while simultaneously resisting expectation of The Internet by not printing Groot.  if you're quietly thinking about how this could be better done in metal---you're right.  And I'll get there someday. Possibly by the end of this build.


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## durableoreo (Dec 2, 2021)

Well, it's been a minute.  Had some family stuff to deal with.  But I escaped to the machine shop today.

The current plan is to make an adapter so my 3PN spindle will take a 3C collet.  The spindle tapers at 20 degrees and 3C tapers at 12 degrees so it should all work out.  Same diameter body, too, about 0.655 in.  The adapter is O-1 steel.  I've been using carbide insert tooling, mainly a boring bar, and getting along well enough. 

After looking all around, I found my compound.  I set the angle with some angle blocks from some budget manufacturer. 







Here is the part.  It's not tested against the spindle yet.








Later I inked the spindle and checked the fit





This is what I found (below).  The pattern is not symmetric, so there is some wear in the spindle's surface.  Not the best contact.  Had to fiddle around for quite a while to straighten this out.








Here's the final fit, which shows better contact. 







You can't see it but the adapter sits fairly high in the spindle taper.  That flange does not sit against the face of the spindle.  It's about 0.100 in proud.  So I need to do a few more passes.  But I was anxious to see if I could cut the taper angle correctly...


Here's the other side of the adapter.  Had some trouble parting off so I eventually used the hack saw (for character) and dressed the edge with a file.  Note the finish.  I later mounted it in the 3-jaw chuck and took another cut to clean it up.  But before that, I tested the fit against the 3C collet.





You can see the ridges from the adapter on the collet. 





After monkeying around with this for a while, I remembered that I planned to do the final turning of the ID in situ.  I'll just mount my compound on the mill's table.  Come to thing of it, I don't need X or Y working to finish the spindle---only to lock in place. 

As of now, the axes are not quite what I want:

X lever
Y lead screw
Z lever
I had been planning to convert the levers (rack/pinion) to lead screws.  But I've been watching Rotary SMP videos and now I wonder if I should convert to ball screws.


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## durableoreo (Dec 4, 2021)

My first attempt failed.  Turns out that I trimmed too much off the outer surface AND my angle was too large for the internal (3C) taper.  It's hard to see but when I pressed the collet into the arbor, the adapter spun freely.  The 3C taper was only engaging at the smallest part of the taper, which was actually on the surface of the arbor.







See the gap... The flange sits flush on the arbor's face when I push it in.  It also makes decent contact on the taper of the arbor.  But the collet bottoms out in the arbor and the adapter floats.  See how the collet extends beyond the adapter (red dot above). Also, the angle inside the adaoter is too large so the top of the collet does not engage with the large end of the adapter spins loosly when the collet is pressed in (below, using the tail stock to apply pressure).



I measured the 3C taper I had cut.  It's not a very good measurement.  It depends on corners contacting the taper and the gages were almost too thick to fit through the part.  Tried 24 deg, which was loose at the top.  23-1/2 deg was worse, 24-1/4 deg was better.  This is consistent with the previous observations.




I cut another part.  This time I had the hang of it and it took about half as long.  I didn't bother trying to get the flange to seat against the arbor's nose and I took care to set up the 12-degree angle accurately.  Also, I left a bit more meat in case I need to touch up the internal taper.  I did cut back the face of the adapter so that the collet stood proud even when pulled in.




To make sure I didn't have the same problem as before, I pressed in the collet and checked if the adapter rotated.  There's a set screw preventing the collet from rotating so I wasn't able to check contact in the arbor.



I was going to harden and grind the adapter but now I'm not so sure.  I wish it was done, which makes me want to skip steps.  That kind of laziness and impatience guarantees a bad outcome. 

Also, I'm thinking about the risk of hardening a part with thick and thin features.  But that's a fear more than a reason.  If I get a bad warp, I'll just make another part.

To do the grinding, I got a fog-buster type system.  I also ordered an air compressor (which I've needed in the shop for a long time). I already have a router type toolpost grinder with an AXA mount, various abrasives, soluble-oil coolant, etc.  Even with all the equipment on-hand, grinding on the lathe will be a stretch.  Maybe that's why I've got half a mind to call it done prematurely.


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## durableoreo (Jan 9, 2022)

A few years ago, Tubelcain posted a series of videos about a drill-press vise.  I made the vise but it basically broke my have-file-can-do attitude.  Since then, I've been trying to bootstrap a machine shop.  I bought this old mill because it seemed less expensive and a million voices on the internet have been preaching the gospel of old iron since I was young.  Now I've been working on this mill, in fits and starts, for a year, and with little progress except for what I've learned.  But I'm getting too old for this.  So I bought a Rung-Fu type mill.  It's the G0755, which is like a big brother to the popular G0704.  




With this, I'm hoping to remedy the get-me-by things I've done.  For example, I made a solid tool post for my lathe.  It literally had saw-cut marks on 2 sides and mill finish on the others.  Now the bottom is scraped, the sides are machined, and the edges are contoured so chips don't collect under the tool holders.  It's de-burred and I even touched up the surface a bit with a Renzetti-type magic sanding block.  It could be better but it's one of my first machined parts.






I've got to get the DRO installed.  Have a butterfly-type tool changer coming, too.  Then I'll tackle some parts for the horizontal mill.  

The grinding project is still in process.  I finally got an air compressor but it was damaged in shipping, didn't come with oil, etc.  I have the parts for a fog-buster setup so I'd like to get that going for grinding the 3PN --> 3C adapter.  

I've also been improving the 9x20 lathe.  I added deep-groove ball bearings in the cross-slide assembly, which is a nice improvement.  I also scraped the saddle to the ways.  Here's the before and after photos.  When I started, I was working in cramped quarters and with makeshift fixturing to hold the part at the right angle.  After a while, I used one of those portable workbenches with a custom-cut 2x4 fixture.  It was a huge improvement.  The finished job is not perfect bearing and the cross slide is not aligned well.  It it off by 0.005 as the cross slide travels 4".  But this is too much to scrape in with my level of experience.  At the time, I only had a single 1-1/8" wide scraper to this was really difficult.  Now, despite it being mediocre bearing, it FEELS so much better.




After scraping the cross slide flat, top and bottom, and parallel, I tried to clean up the top of the saddle.  (Didn't get a picture of the bottom of the cross slide.) It didn't go very well but I was getting quite tired of scraping at this point and was torn between alignment and fit.  





I also worked on a 3" vise that I had purchased for the horizontal mill.  It was around 100 $, off Amazon, HHIP or some such Chinese vendor.  It needed some de-burring and the bottom was not quite flat.  Then I made the rails flat and parallel.  Then I scraped the moving jaw.  Then, to my irritation, I found out that fixed jaw was not the same height as the moving jaw.  But it turned out fairly well and I've used it on the new mill, despite the comic size mismatch






I also purchased a Kipp adjustable-tension knob for the carriage lock on the lathe.  It was so nice that I wanted one for the tailstock lock.  Unfortunately, nothing off-the-shelf would fit, so I made one myself.  Here it is with cold blueing.  I painted the knob (which is 3D-printed) black.



I was also inspired to improve the way wipers on the lathe.  Robert Renzetti did this crazy rebuild of a D-bit grinder a while back.  He made a wiper with a sharp edge which caught my eye.  So I did that for the flat and V ways.  Originally, the rubber was screwed directly onto the casting.  I used the FDM printer to make some enclosures out of PLA.  The rubber was then trimmed to make a sharper edge.  There is a also 1/4" felt backing with an oil hole at the top of the enclosure.  Those are installed and seem to be working.  I also added silicone guarding (Renzetti style), which keeps chips off the ways and leadscrew.





One of the failings of the import lathes is the carriage gibs, which are steel plates with tortured arrangements of screws and set screws.  I noticed that mine don't even touch the underside of the ways.  So I'll eventually need to make tapered gibs.  Like this, maybe:

https://www.hobby-machinist.com/thr...h-tapered-gib-conversion-on-mini-lathe.14406/

And speaking of gibs, the straight gib in the cross slide is a crime against machine fitting.  It's like throwing the proverbial hotdog down a 2-lane highway.  The gib is half the width of the gap AND it rotates badly under the pressure of the adjustment screws.  I'd like to make something that's a little better sized.  I'd even consider modifying the casting to accommodate a tapered gib.  But for that, I might just buy a new piece of cast iron and make a new cross slide.

So, with a big mill to bring in the new year, cheers!  My New Year's resolution is to make some money this year with these tools.  Cheers!


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## jwmelvin (Jan 9, 2022)

I haven’t really followed this thread but I’m glad I looked at it this morning! Good stuff. It takes some effort to document your work and I appreciate you doing so. I’d really like to do some scraping, like you’ve done to your vise. Please keep posting as I’ll be interested.


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## jwmelvin (Jan 9, 2022)

Oh and can you post a picture of your silicone way covers?


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## durableoreo (Jan 9, 2022)

jwmelvin said:


> Oh and can you post a picture of your silicone way covers?



Sure, see the photo below.  Renzetti said McMaster had a rubberized cloth-backed material that was 0.020" thick but I couldn't find it.  This is cloth backed silcone, 6" wide, (3635K64).  It is barely wide enough to cover the ways and lead screw.  Wider is better but the material is fairly expensive and I didn't know if it would work.  I backed the carriage up to the tail stock to measure.  Next time I'll use a shorter piece.  In the picture, that's a 6" chuck and there's no problem working close to the chuck although there are now some rubbing marks.  I'm planning to make a MT3-->3C collet adapter soon, which puts the carriage very close to the headstock but with no chuck in the way, there might be enough space for some folds.




Oh, and you can see the solid tool post mount before it was machined.


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## jwmelvin (Jan 10, 2022)

Thanks. The folds and bunching has kept me from trying this style but I’m still letting it kick around in my thought soup.


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## durableoreo (Feb 14, 2022)

I finally hardened the 3PN-3C adapter.  

In the past, I would use a torch and try to judge temperature by color and quench in cold oil and use my wife's oven to temper.  It's possible and perfectly serviceable for the occasional part but the uncertainty and inconvenience are too much for me.  You see, I want to be a real machinist some day.  So I picked up a Hot Shot 360.  Today I spent about 6 hours breaking it in and heat treating my first part.




I followed the recipe for O-1.  From memory, pre-heat to 1200 oF, heat to 1500 oF, quench in 120 oF oil, and temper at 1000 oF for 2 hours.  The part should temper to R_C 35 or so.  From what I read, that's what pre-hardened 4140 bars are sold as.  You can cut it with a file if you bear down.  I'm not sure if this is the right design choice for this part but it's a starting point. 







Out of the oven, it look fairly bad.  I might put it in the lathe and try to touch it up a bit with an abrasive pad.  I considered tumbling it with abrasive media... that's probably better for my fingers.  The one I have is cheap and loud loud loud.  It's so damn loud that I want ear protection just to get from the door to it's power switch.  But I'd rather not leave it overnight so that will have to wait for tomorrow.

The next step is in-place grinding.  I've been working on this for some time.  I got a Dewalt compressor---the one with 2 small horizontal tanks and a manifold between them.  It was damaged in transit, I think.  After making some repairs, I proceeded to completely overfill the oil and run it for a few minutes.  I stopped it to dink around with the regulator.  It wouldn't run after that.  Lots of foam on the dip stick.  I drained the oil to the correct level, waited a while until the air bubbles had dissipated, and tried again.  It ran for a few seconds and then stopped.  I have not idea what damage I've done but I'm hoping that oil will drain back into the sump overnight and it will work in the morning.  Let me know if there's anything else I should do.

When I have compressed air, I can run the coolant system as I grind the ID of this adapter.  Have a bunch of parts for a pressurized-reservoir import kool-mist type system.  Cool-Moist.


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