# D1-4 on a PM1340



## Gerry (Jan 2, 2020)

I have never been satisfied with the runout on my D1-4 setup. After removing and reinstalling any of my D1-4 chucks they never seem to locate properly. They are every so slightly cocked on the spindle. There is a gap between the back face of the chuck mount and the flat face of the spindle. The chuck seats on the taper and is allowed to cock to one side when the D1-4 pins are tightened. Because of this remounting the chuck is not repeatable. Should the flat face of the chuck back register on the flat of the spindle? Should there be a gap between the back of the chuck and this surface? The closest I have gotten to having the chuck straight is to use shims on each of the pins to hold the chuck proud of the tapered cone. This cannot be right because it bypasses the purpose of the cone. Seems like the flats should meet and the cone center in it's mating recess in the chuck mount at the same time. Using a 12" piece of ground stock, chucked in four jaw and centered close to the chuck there may be 0.005-0.008 runout 8" from chuck.  Adjust here to 0.003" and the chuck end will be out by 0.006 or more.  BTW, the spindle face and the tapered cone are both as true as anyone could hope for, 0.0001 so it seems like the problem has to be the interface between the chuck and spindle. I'd be interested in any comments anyone might have. TIA Gmasterman@aol.com


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## darkzero (Jan 2, 2020)

Yes it should meet the flat face on the spindle & there should be no gap. Nose taper should also register but you obviously won't be able to physically see this without bluing.

Have you adjusted the cam lock pins, does the cam mark line up between the 2 arrows (between 3:00 & 6:00) for all three cam locks? If yes the backplate may not have been machined properly or someone took a face cut on it. Sounds like that's the case since you say the backplate does register on the nose.


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## Bob Korves (Jan 2, 2020)

Very common problem.  Darkzero hit it correctly.  The chuck should seat on the spindle taper at the same time it fully seats to the spindle face.  If not, adjust the chuck to get it correct.  (Not the spindle!  Only gently debur the taper and face if necessary)


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## petertha (Jan 2, 2020)

Its possible to experience that with the occasional lathe accessory. I had that with a new, aftermarket face plate. But a decent quality adapter plate or integral chuck should match the spindle nose exactly right out of the box. As darkzero says, full contact on the taper & simultaneously flush on the vertical face. I hope you don't have a spindle issue like egged or incorrect grind angle. It would be rare & a bad thing. Its a bit of chicken & egg thing now, ideally if you have a known good D1-4 accessory to mount, that would lay the spindle issue to rest.

Here are some pics of my poor boy lapping procedure. I cured a blob of bondo on my known good taper (wax as releasing agent), that became a tool backing using ~ 600-800 wet/dry paper in between. I pre-blued it & went around the periphery so the material removal was visually equal, clean, test on nose... rinse & repeat. I was able to get a nice fit that takes a slight bonk to get it off.

Don't be tempted to use your spindle nose as a lap! If its good & the mounted accessory is bad, now you have 2 problems instead of 1.

You can put an accurate DTI on the spindle nose, rotate & see what you get. Technically this is involving your bearings but it should be very true. It might also turn up a raised burr. Its hard to scratch the nose because its hardened & we always strive to treat this surface with care, but a ding on the surface could be enough.


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## middle.road (Jan 2, 2020)

Have you blue'd it yet to see if it is hitting properly?
On one of my D1-4's 3-jaws that I got with the lathe the pins were NOT mounted/positioned properly and the chuck wouldn't seat correctly.


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## Gerry (Jan 3, 2020)

Thanks for all the comments! Is there some spec for the D1-4 pin stick out. Should they all be the same or within some tolerance? I really do not have a good way to measure the pin cut out location.

To use blue to check for taper interference, would you remove the pins or leave them in place, install the chuck then remove to look for? The issue I have is with all my D1-4 chucks and faceplates. None of my stuff is what I would call "high end" so my issues may very well be in the quality of my equipment-just have to figure out how to make it better


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## Gerry (Jan 3, 2020)

Just went through the process of installing every D1-4 attachment and found that I do not have a single one that butts up the the back surface. Every one leaves a gap anywhere from a few thou to a bit over 10 thou. I would have thought that out of five chucks and a faceplate one would fit right. I also find that the cams in the headstock do not all turn to the same locking point but they are not far enough out to justify adjusting the pin in the chuck a full turn. Is there a way to correct this without risk of going too far? 30+ years ago I had a POC Smithy with the same issues. I ended up turning the nose on the spindle down to make the chucks fit flat but I hate the idea of trying to do this on a good machine to rectify chucks with poor tolerances. Too easy to screw up beyond repair. So, do I need to try to make a cone from aluminum to use to try to lap the chucks to fit? I have dealt with this problem for years by shimming the back of the chuck but I'd rather do things right. Thanks for any suggestion y'all offer


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## darkzero (Jan 3, 2020)

I'm surprised none of your D1 accessories fit. Something is not right. I would not touch the spindle (lapping, etc), that would be absolute last resort for me.

To adjust the pins:

Can't really measure them, not length anyway as they will vary by manufacturer. Most pins will have a line on them. Adjust the pins in or out so that this line is flush with the mating surface on the backplate. Won't be able to get it perfect, just close enough as a starting point.







Then install the accessory on the spindle. Proper lock up should be between the 2 arrows. If you don't have any markings, proper lock up is between 3:00 & 6:00 with 12:00 being unlocked.

If the cam lock does not quite make it to 3:00, remove the SHCS, unscrew the cam lock pin one turn, reinstall the SHCS, try again. If the lock goes past 6:00, screw in the pin one turn & repeat.

Won't be able to get the marks all to lock at the same position cause of how the pins are adjusted (one full turn). As long as they're between the 2 arrows it's fine.


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## ddickey (Jan 3, 2020)

When you remove your chuck(s) do they come right off when the camlocks are loosened or do you have to tap with a deadblow.


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## Gerry (Jan 3, 2020)

To remove chucks have to be bumped to get them to unseat. Camlocks all work as they should. Installed my collet chuck with a 1" bar. Collet chuck(from Grizzly) does not seat on the flat of the spindle. Tighten the camlocks and the chuck goes off center. By adding 3 0.005" shims spaced evenly around the flat I can get the chuck to read within 0.002. Take the shims out and you can see the runout easily. Issue is the same with every chuck. On my 3 jaw, it takes nearly 0.020 shims to get it to run somewhat true. Seems like to run true the recess in the chuck back has to be shimed away from the cone on the spindle. Go too far then the cone is pointless. Have even tried tightening the camlocks in many steps hoping to pull the chuck in centered without luck. I'm not tightening up one then move to the next on to the next, trying to do things evenly. I have even clamped a 16" long piece of stock(in my 3jaw) with a center drilled in the end held in place with my live center and then tightened the camlocks but when I back off on the center the stock moves off center. Shim the back of the chuck and this works much better. Just cannot help but think the issue boils down to different manufacturers not following the same D1-4 specs for the recess that centers on the spindle cone. Never had this problem with my old Sheldon with a screw on chuck. The spindle on my PM runs true within a thou everywhere I check. Thanks again for listening to my problems and any suggestion you can offer


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## mikey (Jan 3, 2020)

It is very unusual for every chuck to not seat on the spindle taper properly. One maybe, but not everything. Chucks are ground to a standard so if they all do not fit properly then it just has to be that the spindle taper is off. You might try checking the spindle mount to see if it fall within specs. If it does not then a call to Matt is in order.


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## ddickey (Jan 3, 2020)

Make sure there is a nice deep relief around your spindle nose.
Also the spindle nose should be 11mm tall/high.
Highly unlikely you'll see anything but worth a looksie.


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## darkzero (Jan 3, 2020)

I agree with Mike, highly unusual for all your D1-4 accessories not fitting correctly. Do some measuring to see if your spindle meets specifications. If not should probably give Matt a call. Is the lathe new (recent purchase)?

Edit: Oops, didn't notice Mike included a link already


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## darkzero (Jan 3, 2020)

Another thought, if you completely remove the cam lock pins & place the backplate on the spindle, will it then make contact with the spindle face?

From all that you mentioned, it sounds like the spindle nose it too large/long. If that's the case I would get it replaced under warranty.


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## Gerry (Jan 3, 2020)

I have to say Matt has been EXTREMELY helpful in the past. Lathe is 10 years old and came with the wrong pitch gear in the thread dial. After trying to thread and failing many times(I am always the first to blame myself for anything that goes wrong) I contacted Matt and he had one custom made to replace the wrong on. Lathe was 6 years old at the time and he was not expected to furnish the right gear because the lathe was way out of warranty but he did. He is a fine fellow in my view, I just hate to involve him unless I have no other choice. I bought the lathe from him in 2008.


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## darkzero (Jan 3, 2020)

Yup Matt is awesome. Always willing to help, don't hesitate to contact him, he's just busy all the time which is unsurprising. He has given me parts for free that were not warranty related. Heck, he even upgraded my DRO display for free & gave me my 8" Vertex rotary table for free, wouldn't even let me pay shipping! Why, I have been wondering ever since but I am forever grateful.

So your lathe has been like this ever since you had? Even though out of warranty should still give Matt a call IF your spindle was machined out of spec. Should never have to use shims, the spindle is the most important part of the lathe, it should be accurate & repeat (unmounting/remounting chucks).


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## Dabbler (Jan 3, 2020)

OK Gerry, I've seen something similar before.  it is _possible _that there is a super simple fix:  Please forgive me, but many guys don't tighten their D1-4 camlock properly and then grind down the spindle, like you were tempted to do.

Please try this procedure, and recheck the shim spacing behind the chuck to see:  1) if the gap disappears, or 2) if the thickness of the shim is less and if it is even.  

Remove the chuck and reclean all surfaces with a solvent and wipes.
Put the chuck on very lightly, so the camlocks 'just catch'.
Rotate the camlocks, one at a time to the same rotation, but not hard (yet). On mine, it 1/2 way to the line and things begin to feel 'just snug' equally.
-- this, believe me is a necessary sub step, forD1-4 and D1-6 camlocks: everything should be lined up at that point.
If you wonder why, it is because if the chuck goes on cocked, it will never seat all the way down, even on perfectly fitting tapers.  that's because the taper is much larger than it is long, and if it is already on diagonally, it cant seat all the way down.

You've checked everything is still parallel and straight.  then tighten each -not all the way, but to about 3/4 of full tightness.
THEN and only then, tighten all the way.

I do this every time I use either camlock -  and the guy who sold me my D1-4 machine reported the exact problem (of course after I paid for it).
When you do the 3 rotations like this it becomes automatic and they align perfectly every time.  I was taught this 3 turn procedure nearly 40 years ago on the D1-6 lathe I just bought.  The tool and die maker I got it from always did this procedure, and the chucks registered perfectly each time and the spindles show zero wear.  And his chucks are always marked so the cams always meet the same studs.

Get back to me if this hasn't improved.  There are a few other things to check.  An offshore chuck adapter On someone else's lathe from a big name company showed the exact opposite problem (taper too loose), but in that case it requred remachining the backplate to make it fit properly.

The chances your spindle is out are miniscule.  the next check is for spindle roundness in half tenths.  That's far more likely than the taper being the wrong angle or too large. If the spindle is out by more than a half or 3/4 tenth , it will lead to the chucks always being on crooked.

If, however you've used the lathe for 10 years by putting your chucks on crooked, you will have worn your spindle out and made it non-round.  This is an advanced fix.


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## petertha (Jan 3, 2020)

Sorry for the grainy picture but somewhat shows the D1-4 relief groove on my Taiwan 14x40. The camlock diagram shows dimension B as 2.5005" but it doesn't show a relief groove. I remember wondering about this before, does B correspond to the theoretical diameter of the extended line intersecting the vertical surface when a groove is present? I can measure mine or take a better picture if you think its helpful. Its not exactly easy to verify the nose angle to the 7-3-30 accuracy, but there probably is a way. But you should be able to caliper the big end, small end & stickout just for a sanity check.

From everything you've described it appears like the spindle is a slightly larger diameter than your accessories. That would explain them all hanging prematurely up on the taper with open gap between the vertical faces. When this happens, the accessory can easily get cocked at an angle because its not mating along the taper. Sucking in the camlocks is just applying more force to a geometry problem (assuming the studs & lengths are all checked out). The other explanation is the accessory tapers are undersize to the spindle. But I get the impression you have tried a bunch of 'proven' ones all with same result? so this seems unlikely. So this is a new lathe where the problem cropped up?

I would do some basic Sharpy marking blueing & just gently push the best fitting accessory on by hand & see what it tells you. You can see by the post#13 chart that dimension B between D1-2,3,4 are significantly different, so hard to imagine the wrong spindle is inadvertently installed. Some of the big bore 14x40's have D1-5 but I'm pretty sure that would be a lot more mismatch evident. Yours sounds close but no cigar.


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## Tired&Retired (Mar 17, 2021)

Sorry to resurrect an old thread, but I think the post I am making should be here instead of starting another thread.  Besides, I don't see a resolution posted here by the original author anyway.

FYI, I have the PM-1228VF-LB lathe and am having the same exact problem. I have 5 different chucks and NONE of them will contact the faceplate of the spindle. They are all seating on the back edge of the taper.  I am discussing this problem with PM right now to see what they can come up with. FYI, two of the chucks came from them, so the premise that ALL of the chuck backplates have been machined out of spec is kind of hard for me to swallow.

And for the record, I did try the above mentioned method of tightening down the camlock pins slowly and alternating among them.  Didn't help.  If the chucks will not contact the faceplate, trying to get the chuck exactly centered on the taper is not my idea of good way to spend my time.


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## Dabbler (Mar 19, 2021)

@Tired&Retired 

 If progressively tightening the camlock doesn't do it,  then the fit has to be the problem. I wish I could be there to have a look.

The next thing I would try is to use a tenths indicator to ensure your spindle taper is concentric and is radially symmetrical.

If it is, I'd do a 'wear test' by taking the chuck that fits best, putting sharpie onto the taper, and put the chuck on, and then remove it.  Check and document where the sharpie has worn off.  Then index the chuck one pin, and repeat.  Do this all the way around.  You might be surprised by what you find.


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## Tired&Retired (Mar 20, 2021)

I  took video the other day to show the various measurements I took.  






I've been speaking with Matt via email and he agrees that likely the spindle taper is out of spec.  He suggested that I lightly and carefully stone the taper at the area it is contacting the chucks prematurely.  I have already used a 3000 grit stone mounted on the tool post at a 7 degree angle to deburr the taper, and in the case of the 3 jaw chuck that did seem to help a bit by reducing it down from 0.004" to 0.002".  The worst of the bunch is the 4 jaw chuck that I bought at the same time as the lathe, which I can just fit a 0.008" feeler gauge between the backplate and the spindle face.  I have already sent back 1 chuck that I mistakenly rejected as being out of spec for runout (I have already apologized to the seller), but the four remaining chucks are showing 0.002" (3 jaw), 0.004" (5C), 0.006" (ER40), and lastly 0.008" (4 jaw).

So I am wondering if I stone the taper to get the 4 jaw (0.008") to fit correctly, what does that do for the other chucks?  Or conversely, if I aim for the 3 jaw (0.002"), will that mean I will still have problems with the other chucks fitting? So what is best to do here?  I'm guessing that I should shoot for the least amount of metal to remove and then just see how things look with each of the chucks.  Going to be tedious, I think.

I will say here that Matt told me that if I screw up the spindle taper in this pursuit, he will send me a free replacement.  But heck, replacing the spindle is probably not something to be taken lightly, so I am doing to be REAL careful about this.


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## COMachinist (Mar 21, 2021)

What I would do is ask for a new lathe don’t do any thing to the spindle or the chucks until you are sure where the lathe is out of spec. I would bite the bullet buy a top of the line chuck, Bison, Gator or pull the back plates and re machine them to you lathe spindle. I did that to my PM12x36t lathe and most of my chucks ha less than a.001 TIR my go to chuck is a Bison 8” with3 tenth run out.
buy good quality and you want have these issues.
CH


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## Tired&Retired (Mar 21, 2021)

COMachinist said:


> What I would do is ask for a new lathe don’t do any thing to the spindle or the chucks until you are sure where the lathe is out of spec. I would bite the bullet buy a top of the line chuck, Bison, Gator or pull the back plates and re machine them to you lathe spindle. I did that to my PM12x36t lathe and most of my chucks ha less than a.001 TIR my go to chuck is a Bison 8” with3 tenth run out.
> buy good quality and you want have these issues.
> CH



So it is your position that the PM-1228VF-LB is NOT a good quality lathe?

Please bear in mind that this is for HOBBYIST level "work".


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## Dabbler (Mar 21, 2021)

@Tired&Retired For hobby work, PM-1228VF-LB will do just fine.  My 12X36 lathe is only a hundred pounds more, and I do some pretty accurate work on it.  Depending on who made it, to what spec, it will vary in quality, but I think PM offers pretty god value for the money.

It is possible to accurately measure your spindle and make the backplates conform to it.  If you screw up, you can always get another backing plate for your chuck.  If you mess up your spindle, then you're hooped.  As I suggested, make sure the nose is concentric, then make your bakcing plates for your chuck conform to it.  Now if you have an eccentric speindle or it is not running radially true, than I'm pretty sure PM will try to make it right.


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## mikey (Mar 21, 2021)

@Tired&Retired, I have a couple of comments for you.

Taking run out readings on a running machine is fraught with inaccuracies and cannot be relied upon to give you meaningful data.
There are only two surfaces that must be accurately assessed on a lathe spindle - the inside taper and the chuck register; ideally, they will be the same. The run out on each surface is typically checked by rotating the spindle by hand and then using a specific procedure to assess run out. If you want to discuss this, we can.
Checking run out on the camlock part of the spindle or the chuck body tells you nothing useful .
Measuring run out of a test rod held in a 3 jaw scroll chuck is totally useless as well because it reflects the accuracy of the scroll and jaws at that single point _of the scroll_; it is not a reflection of the accuracy of the spindle or spindle mount or the chuck.
How tightly a chuck fits on the spindle depends on how the spindle is ground. It also depends on how the chuck recesses are ground. Given that the accuracy of the chuck is determined by how well it fits the spindle register/taper, _how tightly it backs up to the face of the camlock part of the spindle_ is not that critical. In point of fact, you want full contact with the spindle's taper and the chucks female taper when the chuck is locked down. If the rear of the chuck happens to contact the face of the spindle at that point then that's good but if it doesn't then that is secondary to full engagement of the spindle and chuck's tapers. Does that make sense?
Tightening a camlock chuck is simple. There is typically an index mark on the face of each cam. When tightened, each mark should fall between 3 and 6 O'clock. If a particular cam does not fall inside this range then the depth of the stud on the chuck side has to be adjusted to bring the locked cam within this range. You also do not need to serially tighten the cams so many times. Just lightly snug each one once as you install the chuck so it doesn't fall off, then go around again and fully tighten each cam, making sure the index marks fall inside the range I mentioned above.
Given how critical the accuracy of the spindle is, I would be very cautious about touching it unless you have the ability to precision grind it in place. If it is off, better to just replace it but first make sure it is actually off.


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## COMachinist (Mar 22, 2021)

Tired&Retired said:


> So it is your position that the PM-1228VF-LB is NOT a good quality lathe?
> 
> Please bear in mind that this is for HOBBYIST level "work".


If it is made china, yea the quality kind of sucks. Chinese stuff is almost always a project. Their electrical is unreliable, the motors are a joke and the machine finish is really poor.  Oh and don’t let me forget the castings and cast iron is very low quality, as well. It for sure. Taiwan machines, I have not had any problems with them. They are really good vs Chinese.
CH


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## mikey (Mar 22, 2021)

@Tired&Retired, we seem to have lost you. Looking over my previous comments, I wonder if I offended or intimidated you somehow. I assure you that was not my intent; I actually want to help you sort this out so you and Matt can have a meaningful discussion and take appropriate steps to resolve this issue. Then you can move on to learning to use your new lathe.

Measuring the run out of a spindle, be it a lathe or milling spindle, is simple once you understand the methodology. If you are interesting in going through this process, please re-engage and I'll stick with you until the end.


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## Ken226 (Mar 22, 2021)

@Tired&Retired 

Mikey's giving you good info.  He knows what he's talking about.

Think of it like having your fly unzipped, or a cliffhanger stuck in your moustache.  It's a little embarrassing, and you'd rather noone noticed, but in the end your glad someone told you.

Have you tried measuring your spindle nose and comparing the dimensions to published specs?  Its always better to be certain than guessing.  Even if it's a really good guess.    I'll go measure mine in a minute, and post the results.


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## Ken226 (Mar 22, 2021)

OK. This is a quick n dirty drawing, based on measurements i took in a few minutes with a caliper.  figure + or - a thousandth or two.

If your spindle nose is really close, this might not help much.  But, if its way out, you should be able to tell.    If you can take a diameter measurement @ two points, and the distance between those points, calculating the taper will be pretty easy.


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## tq60 (Mar 23, 2021)

Re-read first post, if it is crooked on the taper then the taper is not correct.

It should go on straight.

Have not messed with dx tapers so just guessing, assuming they do not fully seat on anything flat as the taper is the interface.

Maybe there should be a measurable space behind?

Maybe someone with a monarch can provide some reference here.

Sent from my SAMSUNG-SM-G930A using Tapatalk


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## Ken226 (Mar 23, 2021)

tq60 said:


> Have not messed with dx tapers so just guessing, assuming they do not fully seat on anything flat as the taper is the interface.
> 
> Sent from my SAMSUNG-SM-G930A using Tapatalk


On D1 spindles, the chucks do indeed seat against both the taper, and the flat face of the spindle.  As @mikey said, it's a secondary consideration. It doesn't need a ton of force holding the faces together,  just contact.   The taper/register controls radial runout.  The face contact just prevents axial deflection under cutting forces.


The tapered nose itself is too short to provide significant resistance axial deflection due to either cutting forces, or one cam being tightened to a higher torque value than another.

There is less than a half inch of taper, so under significant cutting forces, a gap at the rear of the chuck would cause tension/compression forces be transferred into the cam pins. The amount of deflection would be inconsistent, with 3 spots 120° apart per revolution having more deflection (the gap between the pins.   The pins are (3, on a d1-4)  120° apart.  This would likely contribute to surface finish issues and possibly chatter.

The typical procedure for fitting a chuck that doesn't fully seat against the spindle face, is to mount up a good chuck/collet, then mount a bar into the properly seated collet/chuck.    Then flip the offending chuck backwards,  tightened onto the bar, and polish the inside of the female taper with emery cloth untill it seats with contact on both the taper and face.  A little dyechem helps.  It also helps to remove the camlock pins from the chuck, for safety.

Most of the backplates I've purchased for custom fixtures have needed this done.  Some more than others.   It usually takes be about 20 minutes to get a new d1-4 backplate properly fitted to my spindle.

I used a Shars backplate for the receiver truing chuck I recently made.  It had a couple thousandths gap when new.  A few minutes with some 220 grit sandpaper got it sorted out.





This spider chuck used a chinese backplate as well.  It had a gap, and took about a half hour to get properly fitted.




It would seem that most of the new backplates have the taper made a little undersized, to allow for final fitting.

Several of my chucks were fitted to other camlock lathe's I've owned in the past,  and still fit my current lathe quite well with no additional fitting required.  That implies that the spindles were all the same, and the backplates tapers were undersized.   I've never found a new backplate with an oversized taper. Always undersized.

Only 2 chucks I've purchased ever fit perfectly out of the box.  One was a Kalamazoo 3 jaw, the other was a Chinese 6 jaw.

From Rohm's instruction manual:

Mount the chuck and without tightening the cams there should be a gap of .0008 - .002 inch. The manual states to evenly tighten the cams. The manual then states *"Both the short taper and the face of the chuck must be in full contact with the spindle nose after mounting
*
So, with the chuck in place on the spindle taper,  a gap of up to .002" should allow the cam pins to pull the chuck onto the taper, sufficiently to close the gap and bring the chuck and spindle faces in contact, providing a firm axial register.


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## Dabbler (Mar 23, 2021)

Ken226 said:


> It would seem that most of the new backplates have the taper made a little undersized, to allow for final fitting.



This could be the entire problem.  When I bout my Pratt-Bernerd chucks back in the 80s, they fit perfectly, and I hadn't thought of that one!


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## Ken226 (Mar 23, 2021)

Dabbler said:


> This could be the entire problem.  When I bout my Pratt-Bernerd chucks back in the 80s, they fit perfectly, and I hadn't thought of that one!



I just want to clarify, that was a guess on my part. Based on my experience with chinese back plates always being a little undersized.   I don't know that for certain.

When I've bought nice, expensive chucks, they fit. 

According to Rhom,  when the cams are loose, a gap of .0008" up to .002" between the backplate and chuck face is normal.  Tightening the cams should pull the faces together.   Over .002" might require more leverage than just a chuck key to pull the faces together.  

I don't want to have to use a cheater bar to change chucks, so I like them to have about .001" gap when loose.  After loosening the cams, a gentle smack with a rubber mallet pops them off.


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## Tired&Retired (Mar 23, 2021)

Nope, you all didn't lose me.  Just have other fish to fry and only get back to this when I can.

Yes, I did measure the diameter of the spindle taper at the back edge, as best I could and came up with 2.4800 more often than not.  I haven't tried to measure the front of the nose taper as I doubted I would be able to get a good read there that would mean anything.  I did try to measure the female taper on one of the chucks and came up with 2.4725, but I honestly don't remember which chuck I measured.

As I mentioned earlier, I used a 3000 grit stone rod mounted in a drill fixture which is in an MT3 adapter on my compound.  I have that set to 7 degrees to match up as best I can with the angle of the taper.  I only used slow speed on the lathe, and didn't apply all that much pressure, nor spend a lot of time with it. The idea was just to deburr and possibly polish the spindle nose taper a bit.

So anyway, when I took the earlier mentioned video, I mounted four chucks on the spindle while taking the video.  The other day I was looking at the spindle nose and noticed the marks made on the taper during the process of mounting those chucks and took the picture below with two crops to get a  closer look at the metal surface.













Got to run....


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## mikey (Mar 23, 2021)

The spindle taper is 7 degrees, 7 minutes, 30 seconds. 

7 degrees will not fit.


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## ddickey (Mar 23, 2021)

ISO standards on the diameter of the taper should be 2.5005" +.0003" -0.
The depth of the spindle taper should be .433" +/- .0157". Not that this means much.
Interesting though is the face plate has a tolerance of +.0003/-.0002 on the spindle nose and a taper depth of .3937 with the same tolerance as the spindle.


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## Ken226 (Mar 23, 2021)

ddickey said:


> ISO standards on the diameter of the taper should be 2.5005" +.0003" -0.
> The depth of the spindle taper should be .433" +/- .0157". Not that this means much.
> Interesting though is the face plate has a tolerance of +.0003/-.0002 on the spindle nose and a taper depth of .3937 with the same tolerance as the spindle.



Yea, those are the correct nominal dimensions.   Where they get hard to measure is when they add features such as undercuts, relief cuts, chamfers etc,  at the points where the features are dimensioned.

For example,  the 2.5005" diameter is @ the point where the taper intersects the spindle face.   On my spindle, and most others I've seen, there is a radiuses relief cut there,  and nothing to measure.

  Theoretically, if that relief cut weren't there, the taper would continue to the chuck face, intersecting it at the point where the tapers diameter is 2.5005.

A  chamfer also exists on the nose of the taper, which reduces the effective contact area, but is still part of the nominal length dimension.

It's clear in tired&retireds pics above that his has a relief at the same point as mine.  The theoretic point on his spindle where his taper would measure 2.5005" ,  has a relief cut.


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## Ken226 (Mar 23, 2021)

So, as an experiment, i went out to try and measure my spindle at that theoretical datum where the taper would intersect the spindle face, were that undercut not there.

Heres the undercut:




Here's my setup, using .125" thick parallels and magnets to locate the spindle face relative the the part of the taper measured:




Heres trying to measure the diameter, @ a point .125" from the spindle face. Basically, i tried to measure the taper diameter across the face of the parallels. It took a few tries to get a diameter i was confident was close to correct.  After a half dozen attempts, i settled on 1.469" (probly closer to 2.4694") judging from the pic.   It was challenging, trying to get the caliper jaws flat against the surface of the parallels, so it would contact the taper on the same plane as the parallel face.  I ended up setting the parallels at an angle, like the letter A, so the caliper jaws could lay relatively flat against the parallels.












Then i used my CAD software to draw the taper, and continue the 7.125 degree angle along the z axis for an addition 0.125 inch. Then measured the theoretical diameter at the point the taper would intersect the chuck face, were there no undercut:





@Tired&Retired

Perhaps try a similar measurement.  Arrange the parallels so you can hold the caliper jaw faces flat against the parallels.  Measure the taper diameter @ that point.


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## mikey (Mar 24, 2021)

@Tired&Retired, I was sad to see that you took a grinder to that spindle register. Given that you set it to 7 degrees, even if you only ground a little bit off, no standard D1-4 chuck will interface securely to that spindle because the geometry is now off. I think you should have another discussion with Matt and let him know what you did; I suspect he will agree that the spindle needs to be replaced. Since you'll be in there anyway, you might consider upgrading the spindle bearings to a precision class set (ABEC 5-7 or metric equivalent).


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## Ken226 (Mar 24, 2021)

Given what's stated here:
Quote:
"As I mentioned earlier, I used a 3000 grit stone rod mounted in a drill fixture which is in an MT3 adapter on my compound. I have that set to 7 degrees to match up as best I can with the angle of the taper. I only used slow speed on the lathe, and didn't apply all that much pressure, nor spend a lot of time with it. The idea was just to deburr and possibly polish the spindle nose taper a bit."

Depending on the definitions of "not much pressure" and "nor spend alot of time",  he may not have removed more that a few hundred thousandths.  3000 grit doesn't take much off.     Hopefully not anyway!





@Tired&Retired:

If you'll take a few measurements, I'm more than happy to help calculate the current angle of your spindle taper.  To determine if at least the angle is still (or ever was) correct.

Do you have a DRO?   The gear rack for Z travel is notoriously inaccurate.  Especially when the pinion crosses from section to section on multi piece racks.

Anyway.  I'm assuming you have either a DRO, or a dial indicator you can put on the bed to measure carriage travel.

Put an indicator on the cross slide/toolpost, and zero it against the spindle taper. Point it nice and strait to minimize sine error.  Use a DRO or indicator to make accurate Z movement.   Then move the carriage in the Z- direction 0.250",  and record the indicated value.  Should be doable with a ten thousandths indicator.

Basically,  your accurately traversing an indicator a given distance along the Z axis,  and recording the tapers radial change on the X.   I hope that makes sense.

The angle can be calculated by using the following right triangle formula:

Arctangent multiplied by (change in X divided by travel along Z)

So, in your case,  if the angle is still correct @ 7.125° (7°, 7' 30"),   traversing the carriage .250" should move the indicator needle .03125".

With the calculators angular units set to °.






A .001" indicator will allow you to measure 1/4° increments.  A .0005" indicator will get you 1/8° increments,  and a .0001" indicator will get you about .025° increments.


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## Tired&Retired (Mar 24, 2021)

mikey said:


> @Tired&Retired, I was sad to see that you took a grinder to that spindle register. Given that you set it to 7 degrees, even if you only ground a little bit off, no standard D1-4 chuck will interface securely to that spindle because the geometry is now off. I think you should have another discussion with Matt and let him know what you did; I suspect he will agree that the spindle needs to be replaced. Since you'll be in there anyway, you might consider upgrading the spindle bearings to a precision class set (ABEC 5-7 or metric equivalent).


I described exactly what I did to Matt, and he is OK with it.  Heck, I dunno, but isn't there some difference between "grinding" and "polishing"?  Spindle speed was at the lowest setting on the lathe, which I think is 40 to 50 rpm. As for time I held that 3000 grit rod to the spindle taper, no more than counting to 10, then looking at the finish.  When I say it was at 7 degrees, that is + or - a hair.    I lined up the rod with the spindle taper as best I could by eyeball and feel, as it was being held in a drill chuck mounted on my compound slide.  Then looked at what the indicator on the compound slide showed and it was 7 degrees. As for it being exactly 7 degrees, etc, or 7.125 degrees, heck, I don't know.  I don't think I have anything that could actually measure to that precision here.

Are you all forgetting this is hobbyist level, and I am posting this in a "hobby-machinist" forum?  I guess my wife "said" it best with her expression when I told her that I wanted the lathe to be better than one thousandth of an inch tolerance when I showed her a 0.0015" feeler gauge and I wanted it BETTER than that.  That was the "are you serious" look.   LOL!

Yeah, I want the stuff I work with to be as accurate as reasonably possible, and will make reasonable efforts in that direction.  But for someone(s) to be basically claiming that I ruined my lathe with a 3000 grit polishing stone on a hardened surface with minimal (and I do mean MINIMAL) contact duration and pressure, well, sorry, we are not talking on the save wavelength.  3000 grit doesn't remove all that much material even with a lot of elbow grease.  I used to polish a lot of stuff in the past. I know the value of a light touch instead of getting TOO aggressive.

Anyway, Matt has no problems with what I described here and to him.  He actually advised me to be MORE aggressive on the GRINDING of the spindle nose taper. And if that DOES ruin the spindle, he will send me a free replacement.  So I don't have a lot to loose except perhaps not knowing what sort of headache I would be in for to replace the spindle, of course.

But quite honestly, I am thinking that what are the chances that I would be able to polish/grind the spindle taper and get all of my chucks to fit flush with the spindle face AND the spindle taper, when the gap I am seeing on four chucks is 0.002", 0.004", 0.006", and 0.008"?  I don't see how I could do that with ALL of the chucks by addressing the spindle nose taper.  Or am I missing something here?

Might it not actually be smarter for me to address each and every chuck and polish/grind THEM to get each one to fit as precisely as I am able? 

Of course, mounting them on the lathe so I could grind/polish the female taper of the chucks would be a real challenge for me.  Would mounting a rod in each chuck (which would be a MT5 alignment bar be safe?  I am real leery of just that MT5 taper holding such a contraption in place securely without coming loose and bounding across the floor of my garage and bouncing off of my vehicles. So is there a better/safer way to do this?


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## Ken226 (Mar 24, 2021)

Tired&Retired said:


> Of course, mounting them on the lathe so I could grind/polish the female taper of the chucks would be a real challenge for me.  Would mounting a rod in each chuck (which would be a MT5 alignment bar be safe?  I am real leery of just that MT5 taper holding such a contraption in place securely without coming loose and bounding across the floor of my garage and bouncing off of my vehicles. So is there a better/safer way to do this?



It's easy.  Polish with sandpaper/emery cloth.  Not cutting forces involved.

First, chuck up a shaft.




Second,  clamp the bad chuck onto the shaft.




It looks sketchy, I know.  And it would be, if you tried turning or facing.  But for just polishing inside the taper with emery cloth, it works fine.   Just remove the camlock studs so ya don't break a finger.

It takes some work, you have to keep pulling it apart and test fitting.  But once it fits, it fits forever.






To answer your question.  No,  definitely don't attach a chuck to a test bar that's only held inside the spindle taper.  

If that's all you have to work with, run the test bar all the way through the bad chuck, so you can get at it with a tailstock center.    A tailstock live center securing the end of the bar would be prudent,  to prevent anything from coming loose.  You just wouldn't have as much room inside the taper to work with.


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## Ken226 (Mar 24, 2021)

@Tired&Retired

I just want to clarify something.

When you say you have a gap of .002" to .008",  how much approximate torque do you have the 3 spindle cams tightened to?

When a chuck is placed onto a  properly manufactured, in-spec, d1-4 spindle, loosely,  there should be about a .001 to .002" gap between the spindle face and chuck.    

I have mine set up with about a .001 to .002" gap when loose.  When the cams are tightened to about 20 ft lbs,  the gap disappears.   Some chucks take a little more than others.


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## mikey (Mar 24, 2021)

Tired&Retired said:


> I described exactly what I did to Matt, and he is OK with it.  Heck, I dunno, but isn't there some difference between "grinding" and "polishing"?  Spindle speed was at the lowest setting on the lathe, which I think is 40 to 50 rpm. As for time I held that 3000 grit rod to the spindle taper, no more than counting to 10, then looking at the finish.  When I say it was at 7 degrees, that is + or - a hair.    I lined up the rod with the spindle taper as best I could by eyeball and feel, as it was being held in a drill chuck mounted on my compound slide.  Then looked at what the indicator on the compound slide showed and it was 7 degrees. As for it being exactly 7 degrees, etc, or 7.125 degrees, heck, I don't know.  I don't think I have anything that could actually measure to that precision here.
> 
> Are you all forgetting this is hobbyist level, and I am posting this in a "hobby-machinist" forum?  I guess my wife "said" it best with her expression when I told her that I wanted the lathe to be better than one thousandth of an inch tolerance when I showed her a 0.0015" feeler gauge and I wanted it BETTER than that.  That was the "are you serious" look.   LOL!
> 
> ...



Yes, I understand this is a hobbyist site and that you're a hobbyist. So am I. Speaking only for myself, I was trying to help you to understand a few things:

It is important to understand what you're measuring and how you measure it so that you know where you are and *if you have an issue or not*. Making a diagnosis is important, especially for a hobby guy who doesn't have tons of money to throw around. I offered to walk you through the process and you chose to ignore it, which is totally fine but, well, here we are.
It is important to know which things are critical, like the integrity of the spindle taper, and which things are not, like having the chuck touch the surface of the spindle face when the chuck is fully locked down. On lathes with precision spindles that utilize top tier chucks the back of the chuck mount usually does contact the spindle face when the chuck is locked down but not always. I currently have 6 high end chucks and all of them contact the face of my spindle. I have one Chinese ER-40 chuck that is accurate as hell but it does not touch the spindle face when it is locked down; it still has 0.0001" TIR and I don't care that it doesn't touch the spindle face. 
A D1-4 spindle has a specific taper that allows any D1-4 chuck with a matching taper to mount accurately. In order for that to happen, the taper MUST be accurate; if it is off then the chucks will not fit properly. Can you get a chuck to fit a taper that is off? Yes, you can. Will that chuck move under load? Probably. Enough to matter? Dunno. Should you now begin to modify your chuck tapers to fit your modified spindle in the hopes that they will fit? That's a hole that I would not like to step into.
Here is my best advice to you, and I mean it with helping you foremost in mind. I would stop what you're doing and replace the spindle. Do not modify your chuck tapers because there is a good chance they have an accurate female taper at this point and it is likely they will work fine on an accurate spindle taper. 

In my opinion, it was a mistake to grind that spindle. Matt is complicit in this and I hope he makes good by sending you a replacement spindle because it should have been good in the first place.


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## Just for fun (Mar 24, 2021)

Are all your chucks bad?   That doesn't seem right to me.   I don't know jack really,  so just thinking out loud.  But to me you were on the right track with the Spindle nose taper being the culprit.


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## Ken226 (Mar 24, 2021)

Just for fun said:


> Are all your chucks bad?   That doesn't seem right to me.   I don't know jack really,  so just thinking out loud.  But to me you were on the right track with the Spindle nose taper being the culprit.



I have a suspicion that there may be nothing at all wrong with the spindle,  possibly the chucks either.  I was hoping to hear back about the cam torque question I asked earlier.

The probability of the spindle being out of spec,   but giving such a drastic spread of gaps (.002"-.008"), on so many chucks, is very low.   If the spindle was out of spec, the gap would be similar on most, or all of these chucks.

I knew a fellow once who had a similar problem with a new grizzly g4003.  I went over to his house, and quickly realized what the problem was.   He put the chuck on the spindle and, turned the cams clockwise untill he felt resistance.  Zero torque,  just turned them till they stopped.

Needless to say, he had non-repeatable runout issues,  and a gap.


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## Tired&Retired (Mar 25, 2021)

Ken226 said:


> @Tired&Retired
> 
> I just want to clarify something.
> 
> ...



If you watched the video I included earlier, I showed the procedure I used with all of the chucks I tested.  I first turned the camlocks to just grab the chuck in place, then I went around all three in sequence gradually tightening them until they were "grunt" tight.  Sure I have torque wrenches, but do you think that would make any difference?  I am no hercules, but I think I put pretty good tugs on those camlocks.  Even if torqueing the camlocks down to something like 50 ft/lbs would bring the two faces together, is it really such a good idea putting that much torque on those camlocks?

And btw, the chuck with the biggest gap (0.008") is actually the 4 jaw chuck that I believe is Taiwanese made that I bought from Matt when I bought the lathe. Which I would have though would have been the best of the bunch.  And for the record, even though I believe I may have mentioned it before, with every chuck, the camlock indicators are all pretty much in the center of the arrow indicators on the spindle. The closest gap is on the 3 jaw chuck that came mounted on the lathe when I received it.

Anyway, here is the video again so you don't have to go back through this thread to find it -> 




At timestamp ~2:00 I torque down the first chuck so you can see the procedure I used on all of them.  I tightened the camlocks until they would not tighten any more and then used the feeler gauges to measure the gap.


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## Ken226 (Mar 25, 2021)

Tired&Retired said:


> Even if torqueing the camlocks down to something like 50 ft/lbs would bring the two faces together, is it really such a good idea putting that much torque on those camlocks?


I did see your procedure in the video, it's just difficult to tell how much force someone is applying in a video.  I didn't intend to come off as insulting,  just trying to help.

Just based on what I could see in the video, I suspect I may apply a good bit more torque to my cams than you are.  But, it's hard to tell.

I agree that 50 ft lbs would be abnormal, but it's not unheard-of.  25-30 is the norm.

This is an old thread, but has some discussion on the subject.









						Torque Needed For D1-4 Cam Lock?
					

I have been working diligently on the used G4003 lathe that I bought a month or so ago.   I still haven't made a cut with it, but it's getting closer.  I need to start a thread on the project I've made out of it (teardown, repaint, rebuild, adjustment, refinement).    Anyway, I put the 3 jaw...




					www.hobby-machinist.com
				




I've had them require that much in the past,  which is when I mounted the chuck backwards on a rod, dyekem the taper,  and hold emery cloth against the taper with my fingers  untill the dyekem was well gone, then re-tested the fit.


The square sockets in the cams will take a 3/8" drive extension.  Perhaps grab a torque wrench and try it,  see if 25-30 ft lbs helps at all. 

I'll check mine right quick and post back the results.

Edited to add:

I tried 5 chucks.   All of my well used old chucks (4 of them) pulled tight @ about 20 ft lbs.    A new 6 jaw took 28.   

All of them except the Kalamazoo 3 jaw have been mounted backwards on a shaft and had the tapers lightly sanded to get them to the state of fitment they are currently in.


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## Tired&Retired (Mar 25, 2021)

For the record I didn't try the feeler gauge tests until I had tightened down the chucks as tight as I could get them by hand.  So I don't know the gap on a loosely attached chuck on my spindle. Honestly, I didn't think it would be pertinent.  For instance, if I were getting 0.008" of a gap with my 4 jaw chuck tightened down as tight as I can by hand, what would it matter what the measurement is with the camlocks barely engaged?

BTW, I did put Dykem on the spindle taper when I first started talking to Matt about this, and I believe I used the 3 jaw chuck at the time. There was just a very small wear ring at the back of the taper where the chuck apparently was engaging the taper.  Sorry, I didn't think to take any pics of that at the time.  The 3 jaw chuck appears to be the closest one to being fitted properly to the spindle, as it there is only 0.002" gap at one part of the contact area.  Which perhaps you are right, that just tightening the camlocks further would snug it right up.  But seems to me that the 4 jaw chuck with that 0.008" gap would need a LOT of convincing to snug up.  I would hate to have to use a jackhammer to then break it loose from the spindle.


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## Ken226 (Mar 25, 2021)

Tired&Retired said:


> But seems to me that the 4 jaw chuck with that 0.008" gap would need a LOT of convincing to snug up.  I would hate to have to use a jackhammer to then break it loose from the spindle.



Yea,  I suspect that one is going to be a bit of work, but totally doable.   It takes very little material removal on the taper to get a big movement along the Z axis.  

It's the same spindle, your mounting each of the chucks too.  That the gap is different for each chuck strongly implies that the chucks are what vary in size.   Even if the spindle is a on the MMC (max material condition) side of the tolerance,  the chucks are clearly not all the same size.

The chucks will be the easiest to adjust.  

For example,   opening the chucks taper diameter by .002" will move the chuck .008" closer to the spindle.

Here's the calculation:

Tangent(7.125)(.008)(2)=.001999

Where 7.125° is the taper angle, .008" is the distance you need to move the chuck and (2) converts it from radius to diameter.

The chuck that's only .002" from fitting, would only need the diameter opened up by .0005".   You could accomplish that with about 5-10 second of polishing with 220 grit.

Tangent(7.125)(.002)(2)=.000499


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## Tired&Retired (Mar 25, 2021)

mikey said:


> Here is my best advice to you, and I mean it with helping you foremost in mind. I would stop what you're doing and replace the spindle. Do not modify your chuck tapers because there is a good chance they have an accurate female taper at this point and it is likely they will work fine on an accurate spindle taper.
> 
> In my opinion, it was a mistake to grind that spindle. Matt is complicit in this and I hope he makes good by sending you a replacement spindle because it should have been good in the first place.



So you are saying that all four (4) chucks I checked in the video, with each having 0.002", 0.004", 0.006", and finally 0.008" gaps, respectively, are ALL just fine?  As someone here mentioned earlier, if it was the spindle taper that is bad, then wouldn't there be logical to assume that all four of the chucks would gap roughly the same? Of course, they could ALL be bad, and the spindle taper be bad as well.  With my luck.....

Uhhh.  Using 3000 grit on anything is NOT grinding. Have you ever wet sanded a car's paint job?  If you started out using 3000 grit, you would die from old age before you got the job done. And that is simply automotive paint, not hardened metal you are trying to "remove" material from.  3000 is normally used only to remove the haze that you get from using 1500 or 2000 grit. Which is basically the minute scratches that the coarser grits leave behind.  Extremely fine grits are NOT for gross material removal.  You use the coarser grits for that and always start from the coarsest you believe you need and gradually work up to the finest grit. Use too coarse a grit to start off with, and you WILL regret it. Heck, just using 3000 grit after using something like 400 grit would wear you right out trying to get the finish you are after.  Start off with 3000 grit?  Heck, hope you are retired and lots of time on your hands.

Heck, I polished the aluminum cradles on my vette when I had it in the shop for a drivetrain upgrade.  You just cannot start with something like 3000 grit as that would do nothing but remove just the highest microscopic "burrs" on the metal and nothing more without making a lifelong career at it. Look at the pics I enclosed of closeups of the taper.  All my polishing did was to deburr the presumed microscopic rough high spots off the metal as you can still see the original pits of the metal plainly visible. Had appreciable metal been removed, you would see a completely uniform glossy mirror like surface on the metal left over by that 3000 grit abrasive.  Not to mention it would have taken an enormous amount of time to get there.

If that very light polishing I did has ruined the spindle taper, as you seem to be convinced of, then if that much metal was removed to ruin it, then in what way would it be ruined? How much metal would need to be removed to take it out of manufacturing tolerances?

Heck, for that matter Matt told me he has worked on actually grinding spindle tapers in the past with success, and recommended that I use a much coarser grit than that 3000 I have used, because the 3000 grit would take me forever to remove any appreciable metal.  I don't believe he would steer me wrong about how best to resolve this problem with the lathe I bought from him.  Do you?

So, with all due respect, I just do not agree with your opinion that the spindle taper has been ruined. Not saying you are wrong, just that I do not believe that to be the case right now.

As for getting a replacement spindle, only if I feel confident that it is necessary. At this point, replacing the spindle seems like it would be a hell of a lot of work to correct something that could likely be fixed a whole lot easier.  And as for the suggestion of replacing the entire lathe that was offered a little while back, well, seriously? Maybe you enjoy the time and effort necessary to pull the lathe off the table and put it into the back of the pickup truck, recrate it, take it for pickup by UPS (they cannot get a large truck up our driveway), then wait till a replacement comes in and then do the reverse to put the new one in, but I surely don't. Honestly, if that were the case, I would probably just use the lathe as a horizontal polisher on rods and poles and be done with it.

That being said, thank all of you for your suggestions and offers of help. I AM reading everything, but honestly I cannot act on it all. I am looking for the best and easiest solution even though the two might possibly be mutually exclusive.


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## Tired&Retired (Mar 25, 2021)

Ken226 said:


> Yea,  I suspect that one is going to be a bit of work, but totally doable.   It takes very little material removal on the taper to get a big movement along the Z axis.
> 
> It's the same spindle, your mounting each of the chucks too.  That the gap is different for each chuck strongly implies that the chucks are what vary in size.   Even if the spindle is a on the MMC (max material condition) side of the tolerance,  the chucks are clearly not all the same size.
> 
> ...



Well a bit technical mathematically for my old brain, but sounds like this may be the best path for me to take.

I do like the suggestion about using the tail stock to hold the MT5 test rod in place, as I really didn't like the idea of the weigh of a nearly free standing chuck spinning around at even slow speeds. Even just having one just drop on my foot would pretty much ruin my day. Not to mention that rod flailing around that the chuck is wrapped around.

My attitude when running the lathe is that the SOB will kill me if I let it.  

So I am trying hard not to let it get the chance.

Thanks!


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## Ken226 (Mar 25, 2021)

Perhaps its just a little tolerance stacking, combined with a couple chucks that are a bit outside of the acceptable tolerance range.

According to this, from Pratt Burnerd Chucks, the taper large end is 2.5005"  with a tolerance of +.0005 -.000.    So, a diameter from 2.5005" up to 2.501" is acceptable.





I can't find anything indicating that the taper in the chuck would have a different tolerance.  I hate making assumptions, but in the absence of evidence to the contrary, if i assume the hole in the back of the chuck is toleranced the same.  2.5005" +.0005 -.000,  the hole diameters from 2.5005" to 2.501" are within spec.




So, if your spindle happens to be on the maximum material condition side of that tolerance with a diameter of 2.501",  it would still technically be within spec.   In that case, a chuck with a taper diameter of 2.5005" would be withing spec as well.


Using a little simple trig,  that .0005 diameter difference on the tapers results in a spindle face gap  of .002".  Everything is within spec, but on opposite sides of the tolerance allowance.  This jives well with the info a couple pages back published by Rohm chucks.


Now if your spindle taper is on the MMC side of the tolerance @ 2.501" AND one or more of those Chinese chucks/backplates have a taper that happens to be undersized, even by just a little, you have a bigger gap.
In the case of a MMC spindle nose and a chuck that has a hole within spec @ 2.5005",   leaves a gap of .002"
In the case of a chuck has a hole that is .001" under minimum spec, you would have a gap of .006"
If the chuck has a hole that is .0015" under minimum, the gap would be .008".    

.0015" of diameter can be polished off quickly with a little emery cloth. 

Don't polish off too much though.  You don't want zero gap,  you want a gap of around .001".    

Up to .002" is acceptable, but no less than .0008".   On my chucks, I aim for .001,  which closes up with about 20ft lbs of torque on the cams.


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## Dabbler (Mar 25, 2021)

@Tired&Retired I have finally gotten to your video.



Tired&Retired said:


> So you are saying that all four (4) chucks I checked in the video, with each having 0.002", 0.004", 0.006", and finally 0.008" gaps, respectively, are ALL just fine?



-- Absolutely you have proven the chucks' backing plates are at fault.  There is no question in my mind about this and if I were there I'd do the same tests.  After seeing the results, here's what *I'd* *do* in my shop were this the case:

First I'd take 4000 grit emery paper and a wooden stick, like a paint stirrer, and run the spindle at 1000 rpm, and polish the entire spindle taper.

*Ok guys before you flame me let me explain -- *

Using 4000 grit for polishing is only going to take the peaks of all those scratches off of the taper.  With 5 minutes work, and changing the paper to fresh a lot, you'd be very diligent to take one tenth off the taper.  Use 6000 grit if you are squeamish.  This will help eliminate any 'hangs' on the taper.  Why wood? because it won't change the taper at all,  not one bit.  I've been honing inside and outside tapers for 40 years using similar techniques, in order to get sub tenths accuracy.  I've done this many times on outside Morse tapers , to repair peoples drill chuck tapers, etc.

This isn't going to fix your problem, however, this is just 'insurance' so the next operations will work well.

Mount your 4 jaw chuck, and dial in the largest round stock you can manage.  You want it to be very well centred, but not necessarily perfect.  the round stock has to protrude the depth of your 3 jaw chuck jaws, plus, say 1/2 inch.  For example a 2" cold rolled bar 6" long with 3" protruding.

Then clamp your 3 jaw chuck on this* with the camlock pins removed*.

Now dial in your taper on the backing plate of your 3 jaw chuck, using the 4 jaw adjustments.  It can be out a thou if you like as this won't matter too much, but ten thou would not so good...

Now you will need a dowel, say 1" diameter, 6" long and you put 1000 grit emery paper around the half of it protruding enough you can grasp it. Run your lathe at about 300 rpm, and 'rock the paper lightly until you get even contact.  Polish the taper for a few minutes and see if you get starry pattern on it.  If that is the case, then your inside taper was never ground or poorly ground.  If it is bright and shiny, well it was ground wrong.  not impossible for an offshore backing plate.

If you are determined to fix the problem yourself, then do this:

You are going to repeat the following steps a lot of times, in order to be careful.  Do not rush these steps...

Reinsert your camlock pins.
Remove the assembly by releasing the camlock on the 4 jaw.  I use masking tape to ensure I remount using the same pins.
Mount the assembly as a 3 jaw chuck (taking care to hold up the assembly to prevent cocking of this heavy assembly]
Note how close you are getting using your feeler gauges.
    - when your tightest is very close you remove it and check how far your are away when the backing plate is 'half tight'.
    - your goal is to get that around 3 or 4 thou, or as close as 2 thou won't hurt.
Flip the assembly around so the 4 jaw chuck is mounted.  Check that your 3J taper is close to concentric, and fix if necessary.
Rehone using progressively higher grit counts until you have your 2 to 4 thou 'half tight.

When you are at a good spot, you will find that your tightening will be fairly easy, and then suddenly get harder.
This is a sign that you are seating on the flat.  You can check with a strong light to be sure there is no light at any point between your backing plate and the spindle flat.

-- That's what I'd do, after all this is all fun, right?

Then I'd repeat it for all my backing plates.


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## Cadillac (Mar 25, 2021)

Did you ever try mounting the chucks without the pins in it? I know you can’t pull them in but maybe the pin holes are to short and not allowing the chucks to seats?  I’d just check all avenues first before sanding the spindle. 
  Another thing is in your video you showed a gauge on all the critical surfaces. To me the flutter was about equal including the inner taper. That would say to me the problem is in the spindle or the bearings. Seeing as your have fitment problems it’s probably the n the spindle.


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## Ken226 (Mar 25, 2021)

^^^^^^^^^
Dabbler gave good advice.  That's what I do as well. 

If fact, when I buy a backing plate that was made[Edit] Offshore, I just assume that It will need done.  It pretty much always needs done if unless your buying $$$ stuff.


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## Tired&Retired (Mar 26, 2021)

OK, some more food for thought with the above posts.

FYI, I broke out the torque wrench and I am getting roughly 25 ft/lbs when I tighten down the camlocks by hand.  So I tried torquing to 30 lbs on the 3 jaw chuck and I was unable to get a 001.5 feeler gauge anywhere between the backplate and the spindle face. So things were looking up!

Then I tried the 4 jaw chuck, which has the largest gap of 0.008".  Best I could do is to bring the gap down to around 0.006".  BTW, both chucks were a bit more difficult to get off of the spindle after the torquing.  I have a 5C chuck and ER40 chuck that are just barely larger in diameter than the spindle, and I already have to work at getting them off of the spindle.  Not really keen on having to use a pry bar on them.  

Thinking of the above mentioned gap on the 4 jaw chuck, as per the recommended procedure by Dabbler, if I am unable to get the 4 jaw chuck to fit properly on the spindle with that large of a gap, is even "truing" up the jaws going to help much?  Unfortunately the 4 jaw chuck is the worst of the bunch concerning the gap I have been talking about. Since the jaws don't hold a shaft or rod at a single point of contact, but along the contact surfaces of the jaws, wouldn't there be the possibility of front to back wobble in the work piece if the backplate of the chuck and spindle face aren't exactly parallel? So even if I got the single plane diameter of the shaft or rod concentric on that one plane in the 4 jaw chuck, won't the rest of the shaft be wobbling around in relation to that plane because of the gap at the backplate/spindle faceplate surface being transferred to the jaws? Or am I missing something here?  I can see this in my mind easier than I can explain it in words.  But I don't always trust my mind lately. 

Let it be known, in case anyone hasn't figured this out yet, I am NOT a machinist. Never even stayed at a Holiday Inn Express.


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## Dabbler (Mar 26, 2021)

Hi 'Tired -  Unless you are registering against the front flange - that is you only touch the taper - you won't get good finishes and you won't have the full strength and rigidity of the spindle.  Especially for parting it will make a big difference.

You won't make things worse by polishing the back plates.  it only can get better.  The only care you have to take, and why I recommended wood - is to not alter the angle of the taper in the backing plate.  Even if it is wrong, you haven't made it worse.

Based on your measurements in the video, your 4 jaw chuck will be working well within expectations for a hobby machine if you seat it against the flange. Your 3 jaw chuck won't be quite as good, but that's what you get with mid-range offshore chucks. - Frankly I've seen worse. Even on a brand new offshore 3J chuck seating properly.

I think we can get really good performance out of your collet chuck once it is seated well.  There are ways to make it better, but out of the scope of this thread.

P.S. - you only 'true up' 4j chuck jaws in extreme cases of wear and neglect.  Truing up 3J chucks is out of your skill range today, but perhaps soon you can consider working on it.


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## Tired&Retired (Mar 26, 2021)

Cadillac said:


> Did you ever try mounting the chucks without the pins in it? I know you can’t pull them in but maybe the pin holes are to short and not allowing the chucks to seats?  I’d just check all avenues first before sanding the spindle.
> Another thing is in your video you showed a gauge on all the critical surfaces. To me the flutter was about equal including the inner taper. That would say to me the problem is in the spindle or the bearings. Seeing as your have fitment problems it’s probably the n the spindle.


When setting up the camlock pins in the chucks, I always would put them where it seemed optimum, and then try them one extra turn in, and then one extra turn out to make certain I had them correctly positioned.  If the holes were drilled short, I would think I would not be able to run the pins in that extra turn?

I guess it is certainly possible that I have multiple problems. The spindle could be machined incorrectly, and ALL of the chucks not being machined correctly, neither.  Honestly, of all the chucks I have, I would have thought that the Precision Matthews name brand 4 jaw would be the closest to being a perfect fit. After all it is supposed to be made in Taiwan, and claimed to be "high precision". But I am just not seeing that, I guess.

I asked Matt for a proven GOOD backplate for the D1-4 spindle so I could have something to use as a test reference, but he did not make any offer to supply something like that to me.  I would certainly return it, but I guess he just doesn't have something like that available.

Sigh, I have wanted a larger lathe for a long time, and was REAL excited about getting one finally.  But that is really losing it's luster right now. 

Actually this headache started even before that when I bought a "Chinabay" lathe that sounded real nice but turned out to be a real bucket of thrown together defective components.  Sent it back and got a full refund, then now I had my appetite whetted decided to take a big step upwards in price and hoped for quality with something better.  Please don't ask me how that is working out for me. I have been on the internet since something like 1997 and have never resorted to profanity in writing.  I sure would hate to break that streak now.


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## Ken226 (Mar 26, 2021)

Fix your 4 jaw first.  It's your most useful chuck, and can be used to fix the rest.


To fix the 4 jaw,    do this:

Take a measurement in the 4 jaw chuck that your about to start polishing,    for future reference..  use a parallel or something precise as a spacer.   This will enable you to keep track of how far you need to go later, while your sanding.  The spacer will allow your caliper jaws to measure the same spot in the taper,  now and later





put your 3 jaw on the lathe and chuck up a piece of bar stock.   Preferably 1" or more.

Turn your 4 jaw around backwards and mount it to the bar.  Indicate it to center,  remove the studs from the back, and start  polishing the inside of the taper with emery cloth.   

Stop occasionally, grab your spacers and take a measurement.    Once your removed about .001",  test fit it.      Now, you'll have an idea of how long it took to remove .001",  and how much further you need to go.

I'll go shoot a quick video for ya.


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## Dabbler (Mar 26, 2021)

@Tired&Retired The chucks might be the best quality Taiwan chucks, but your backing plates might not be -or they can be the best quality Taiwan backing plates, and still might be a little out.  Even the best manufacturers can have a below standard item sneak through.  (I have 14" Pratt Bernerd chucks, and my 3J took a little work)...

I have reached out to Matt to see if he can sell you a proven, ground, (kind of certified, if you like) backing plate as a test sample.  You and he can then negotiate if you might like to keep it, or make some kind of adjusted return.


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## Dabbler (Mar 26, 2021)

Ken a few words - I think your are being really helpful and I appreciate that, and I hope you don't take them the wrong way.

First, if he takes .001 off he will advance his chuck more than 16 thou, which is more than double what he needs (a 7 degree+ taper is about an 1 in 8, and since you are dealing with a half taper it is slightly more than 1 in 16)

Second we are talking about changing things in tenths or half tenths of a thousandth of an inch.  you will never get that resolution out of calipers, and you won't get repeatability appropriate to the requirement.  The only approach is to fit and repeat.  Even bluing in and or 'wear marks' on magic marker is too finicky to do this fit-up. 

By taking a surface polish and trying it, he can slowly zoom in on his solution.   It will take time, but that builds experience.


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## Ken226 (Mar 26, 2021)

I don't take it the wrong way.   I calculated the amount using Autodesk software, using modeled parts.  According to the drawings available online, the taper is 7.125° per side.  14.25° included.  I posted the equation I used to double check my CAD drawing in a previous post,  so others could point out any oversights.  If I made a math mistake, I love to have it pointed out, so I can correct it and avoid it in the future.

I admit,  it's possible I made a mistake somewhere though.   But when doing a quick calculation using trig,  I get the exact same numbers that CAD gives me.

And,  hed be measuring a thou in the taper, not ten thousandths.  

Also,  I'm not suggesting that he skip test fitting,  as often as he likes.    I'm suggesting taking measurements  helps avoid big mistakes.   With a caliper I can tell if I've went a thousandth,  without one I have no idea whatsoever.


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## Ken226 (Mar 26, 2021)

@Tired&Retired

Here's an example of what were suggesting.   Whether you take measurements as insurance or not is up to you.  My education and background is in mechanical engineering,   so I tend to obsess over numbers, but this isn't an especially difficult job.


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## Dabbler (Mar 26, 2021)

I now understand where you are coming from.  I'm just overworried about taking things very slowly.  One guy I tried to help - it didn't work out well.

My mistake on the taper.  I'm sorry for getting it wrong.  on 7 deg 7 1/2 minute it is  a 1:8 taper approx...


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## Ken226 (Mar 26, 2021)

Dabbler said:


> I now understand where you are coming from.  I'm just overworried about taking things very slowly.  One guy I tried to help - it didn't work out well.



Of course. Taking it very slow is absolutely the wise and prudent course of action.   When I board the Lufthansa A330 for that arctic route up and over, from Seattle to Frankfurt,  I'm always hoping the guys at Airbus took it slow and got it right     ,  for  4 hours there's nothing but sea ice down there.

You guys have given the OP excellent advice.   I'm confident he'll have it sorted out shortly.


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## Tired&Retired (Mar 27, 2021)

Ken226, thank you for creating that video for me to look at. I do appreciate it.

Would a plastic rod to wrap the emery cloth (or equivalent) be OK?  I know whenever I would do actual polishing, I liked using something that would present a uniformly even surface to the work so I wouldn't leave streaks in the finish.  Truth be known, I would rather rig up a holder on the compound slide on the lathe and just keep my fingers away from any and all moving parts. I'm not real good at playing the piano, but I do enjoy noodling around on the keyboard now and again. So I can't afford to lose or damage any of my fingers and become even worse at it.

One question, though.  The thinnest feeler gauge I have is 0.0015".  Would eyeballing the gap (or lack thereof, hopefully) be enough to determine that I am actually getting the 4 jaw chuck snugged up to the spindle face? Or is there some sort of machinist's trick to do that?  Actually, thinking about it, I'm not sure I could even look for a gap using a backlit light source. Seems to me the back edge of the 4 jaw chuck actually extends back a bit towards the spindle.

And Dabbler, thank you for reaching out to Matt about this.  He is well aware of my thoughts on which way to bounce with this. We first discussed working on the spindle itself, but my last email to him indicated that I was thinking of backing away from that thought and working on the chucks instead.  But I am not really married to any idea quite yet.  I'm not really ready to actually DO anything until I feel like I have all the ducks in a row that need to be lined up first, and my path is clear in my head.

Thanks to you all for helping me.


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## davidpbest (Mar 27, 2021)

Cigarette wrapping papers are about 0.0003”.


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## Dabbler (Mar 27, 2021)

Great video, Ken!


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## Dabbler (Mar 27, 2021)

@Tired&Retired You are better off using a piece or rounded wood, wrapped around with emery, than trying to use a compound.  It will keep your hands 2-3" away from the spinning surfaces. You can also slow it down to 200 or 120 RPM, and that will feel safer.   If you want to get arcane, you can bond the emery to the wood, but it is completely unnecessary..


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## Ken226 (Mar 27, 2021)

Dabbler said:


> @Tired&Retired You are better off using a piece or rounded wood, wrapped around with emery, than trying to use a compound.  It will keep your hands 2-3" away from the spinning surfaces. You can also slow it down to 200 or 120 RPM, and that will feel safer.   If you want to get arcane, you can bond the emery to the wood, but it is completely unnecessary..



This is the ideal method in my opinion.  It has several advantages,  including safety.

The cast iron common in backing plates will quickly wear the sanding abrasives.  As the sanding abrasives wear and fill,  you can easily rotate the dowel, exposing fresh abrasive material.  Then, you can flip it and use the other end.  

A rectangular section tool has 2 even smaller contact patches.  They would wear and load up very quickly.   A dowel is the way to go.


Keep in mind how small the actual contact patch is on a circular section abrasive tool.  It's bigger than the corners of a rectangular tool, but still small.  Mounted rigidly in the toolpost, You'll be wearing out each spot and having to loosen, rotate and re-tighten alot more often than is necessary.


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## Tired&Retired (Apr 24, 2021)

Success!  At least I think so.

First off, in preparation to doing the actual work on the spindle taper:






I wanted to double check all the runout measurements on all surfaces to have a baseline as to what exactly I needed to do.  Plus I wanted the Dremel tool mounted to the toolpost to be aligned to the spindle taper as closely as I could get it.

I worked on the lathe a day or two later, and I believe I now have satisfactory results.  I was worried about the spread between the 3 jaw chuck's gap (0.002") and that of the 4 jaw chuck (0.008"). But I think I hit the sweet spot grinding the spindle taper for both of them.  The 4 jaw chuck seems to fit flush when I crank down the camlocks using a socket driver instead of the key wrench. At least I can't get a 0.0015" feeler gauge between the surfaces. That is the thinnest material I have in order to try to do that.  So I am hoping the surfaces are actually clamped together now, and there isn't something like a 0.0013" gap there. I can't see any daylight between the surfaces, but the outside rear lip edge of the chuck doesn't give me a real good angle to see any possible gap very well.  Takes some solid whacks with the plastic headed mallet to break it free from the spindle.  I didn't want to chance taking off any more metal, but I did polish the spindle taper surface a bit with a very fine grit after checking the fit with the chucks.

With the 3 jaw chuck, it will actually pop loose from the spindle when I loosen up the camlocks but there doesn't seem to be any lateral play at all that I can tell.  At least when I put a milling bit in the jaws, the runout hasn't changed at all, even trying all three different positions for the camlocks, so repeatability seems to be OK. I tried different diameter bits in the jaws, and best I could get was around 0.0045" out of any of them. It was most often around 0.006" with most of the different diameter bits I tried.  But in any event, I don't  believe that runout is being caused by the chuck not fitting flush against the spindle face any longer.

The other two chucks I have remaining after sending others back to the sellers (ER40 and 5C collets) fit snugly and require modest persuasion with a mallet to break them free of the spindle taper.  Runout for both of those chucks on the inside surface where the collets reside dramatically improved with that now being right around 0.0005".  So that isn't bad at all. For me, anyway. While working on this, I spent considerable time working on that little bit of runout out on the spindle taper noted in the above video and I think that helped make a difference.  All in all, I spent roughly 3 days working on this. So obviously I was taking my time.

So it appears I may have this problem behind me now.  I am REAL glad I didn't have to replace the spindle. I think that would been a real PITA to do.

Anyway, just providing a followup if anyone is still interested.  Thanks for all of the advice and help with this, but I decided working on ONE part (meaning the spindle) was better done than working on all of the chucks.


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