# What are the most cost-effective modifications to a Grizz or HF mini-mill?



## HMF

A question to those of you who own mini-mills. 
Which are the most cost-effective modifications that you can make to a HF or Grizzly Mini-mill?

DRO? X\Y\Z scales?
Column Stiffener?
Head Counter balance?
Fixing the gibs?
Power feed?
Belt drive?
Install Delrin washers for the Y-axis leadscrew instead of thrust bearings?
CNC?
Tormach quick change tooling?
Belt drive conversion from LMS?
Spindle lock from LMS? 
High quality custom bench?
Get all surfaces \ moving parts remachined &amp; add a column support?
Fitting thrust bearings to the spindle?
Air spring?
Bolt mill to a slab of granite?


Let us know what is on your list of TOP modifications!

Best,

Nelson


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## Starlight Tools

Upgraded to a Knee mill!

Walter


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## joebiplane

I have the Grizzly version of the SX3  I am new to serious machining and used steel for the first time on the Steve Bednair version of a Ball Cutter which is half done. I can live with most of the compromises in the machine such as No power feed ...etc. and I am very happy with it BUT  i sure would love to have X " Y DRO ( it has a Z dro as standard..  But I can't spend 600 for a kit to add Y &amp;X dro.. but it sure would be nice.. a stiffer column would be helpful but it is manageable for me so far.  any tips for ACCURATE dro on the cheap???
The unit on the Z axis is really just a digital caliper bolted th the unit.....close to dro ...But no cigar


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## Fuzzbean

Probably the cheapest and easiest thing I did for a big payoff was to buy a longer rack from LittleMachineShop, one that had no mounting holes, and put that on my column to increase the "Z" travel and capacity. I only used 2 screws to mount it, one top and one bottom, so in typical use the pinion does not go over the weaker drilled areas of the rack when under any load. This gives over an inch more "Z" that is fully usable for machining, plus maybe another inch where the head slide is partly off the dovetail but still legit for changing tools or hopping over obstructions.

But it is almost a flat out requirement, in my opinion, to brace the column up. The stock column mounting arrangement totally a joke... I can't imagine what they were thinking.

As far as what I would not do, I never saw the point of the air spring conversions... the torsion arm on mine works good enough, and allows the extra "Z" travel I added without a problem. Belt drives seem attractive until you see how they increase spindle speeds compared to the stock low gear. I like working in steel, and I need the torque and low speeds. The stock spindle lock seems great to me; lots of mill/drills and even smaller knee mills would die to have a spindle lock as simple and effective and convenient as the mini-mill comes with. And CNC... well it sure seems like a waste of time putting CNC on such a flimsy machine.


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## Wheels

Allthumbz link=topic=1403.msg7534#msg7534 date=1301000283 said:
			
		

> Let us know what is on your list of TOP modifications!


Poor mans modifications¦

Number 1 was wheels and leveling jack screws under the stand.
http://i131.photobucket.com/albums/p315/96FXD/Drill Mill/wheels760.jpg

http://i131.photobucket.com/albums/p315/96FXD/Drill Mill/BlackWheels760.jpg

Number 2 was a handle on the motor plate.
http://i131.photobucket.com/albums/p315/96FXD/Drill Mill/MotorHandel2780.jpg

http://i131.photobucket.com/albums/p315/96FXD/Drill Mill/MotorHandel3780.jpg

Number 3 was adding a oil drip gutter under the screw. Now when I oil the screws I don't get oil all over everything in the cabinet stand, it runs out the back. 
http://i131.photobucket.com/albums/p315/96FXD/Drill Mill/OilGutter780.jpg

http://i131.photobucket.com/albums/p315/96FXD/Drill Mill/oilgutter2780.jpg

Number 4 was adding tooling racks to the door on the cabinet stand.
http://i131.photobucket.com/albums/p315/96FXD/Drill Mill/cabnet780.jpg

Then I had to screw down this cover that came off the first time I used it.
http://i131.photobucket.com/albums/p315/96FXD/Drill Mill/Motorhandle.jpg

Next, will be poor mans DRO's

I'm always in search of links with details and thousand word photos of poor mans DRO set-ups.
That could be an entire thread itself.


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## 0369

HF X2, I'm in the process of making a belt conversion, stiffening the column, power feed for the x axis, and will add DRO in the future. Mine ran almost 2 years before the dreaded gear explosion.


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## Hawkeye

I can echo what 0369 says. My X2 equivalent went several years and suddenly threw gear parts everywhere. I made up a 2-speed belt conversion using lathe-cut aluminum pulleys and a sewing machine belt. It's SO much quieter. Well worth doing. Don't wait for the explosion.

I added a reversing switch to the motor control. It comes in handy when I want to use power to start a tap. The DC motor control run dead slow will start to cut just enough thread before it kicks out to guide the tap for hand threading. It's nice to have the reverse to back out the tap. Easy to do with a DC motor.

Other than that, all I've done is add a dial indicator to the spindle, and, of course, the metal stand when I had to get rid of the bench it was on to make room for the shaper. The stand still needs a bit of work - a bit shaky. 

I have a 25-size mill/drill, but I'm keeping the mini because it's handy to do a quick operation without resetting the 'big' mill.

Mike


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## hq308

Mike if it's at all possible I'd be keen to see pics of your belt drive conversion. I've already replaced one gear I broke in my X2 clone and I looked into the little machine shop belt drive but it's not going to fit mine without some major mods. I plan to make my own conversion at some stage and I'm keen to see what others have done.


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## Paradude54

I'm in the process of getting a new knee mill set-up in my shop, but for years I used a Micro Mark mini mill and did all sorts of things with it.  The only modification that I ever made to it was scraping and lapping the gibs.  I even built an AR-15 from a forging on it, but I did have to have a friend with a full size mill drill and tap the buffer tube hole.


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## 110octane

Everyone who has one of these "mill-drills" or buys one (fitted with R8 or other collet system with a draw bar), be sure and check the draw bar out.  I had an ENCO in the '90's with R8 collet spindle and the 7/16-20 draw bar. After using the machine for about six months, I tightened a collet holding an end mill.  I felt the bolt turn just a "little" bit weird, but I thought (Dah!) that the collet had just pulled up on the taper.  After a few passes the collet dropped out of the spindle with no warning and went by me across the shop.  I was lucky.

Examination showed that the draw bar was two piece with the hex nut fixed to the bar with a solid (tapered?) pin.  The assembly had been blued or surface treated and the ends of the pin were virtually impossible to see without very careful study.  The "slip" I felt was the pin beginning to shear. I immediately turned up a solid draw bar on my trusty Logan 10" lathe.  Don't let this happen to you, that thing could have really hurt!

I sold the mill-drill in 2000 (Y2K!) and bought a Grizzly knee mill.  This is a step up and at that time the price was right.  It is a 9 X 42 (I think) and the head will rotate but not swivel.  I really like this machine.  Needless to say the first thing I did before I pulled up any tooling in the spindle was to check the draw bar - yes, it is one piece.  Be safe, Geoff


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## jocat54

knudsen said:


> These are about the same thing as your Z DRO, Joe, but they fit the cheap part of the bill:
> 
> http://www.amazon.com/iGaging-DigiMAG-Magnetic-Digital-Readout/dp/B003JUII2A
> 
> As you can see, Quint Graphics sells them on Amazon. They have different lengths. Grizzly sells one or two sizes. Info: http://www.igaging.com/page97.html Well, not much info.
> 
> I searched and searched and finally found someone who used them on a mill. Guy said they were pretty good, but kept going to sleep and was annoying. These cost about the same as a long digital caliper on sale at HF, so I was going to go for it, then bought a knee mill. I did make a Z axis from a cheap caliper before I knew of these, and it worked OK, but as soon as I added the Z counter weight, so Z axis didn't totally suck, I found I was just reading the dial instead of the DRO. I never put it back on after belt conversion.




These are the ones I installed (3) and really like them.

Also installed the air spring kit from Little Machine Shop and it has been well worth it IMO.


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## squidly87

The only mod I have done up to this point was to add the air spring kit from LittleMachineShop (with the longer rack). The longer rack has helped out with a couple of projects already and there is no more head drop thanks to the air spring kit. 
My next mod will be the belt drive but at the speed I work that may be a while.

Randy


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## Pitchfire

From the list, I'd say a QC collet system or cheap DRO's if you plan on staying with the cheap ones. If you plan to upgrade in the future I wouldn't waste time mounting the cheap ones now, I'd move on to something else and wait.


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## Walt

110octane said:


> Everyone who has one of these "mill-drills" or buys one (fitted with R8 or other collet system with a draw bar), be sure and check the draw bar out.  I had an ENCO in the '90's with R8 collet spindle and the 7/16-20 draw bar. After using the machine for about six months, I tightened a collet holding an end mill.  I felt the bolt turn just a "little" bit weird, but I thought (Dah!) that the collet had just pulled up on the taper.  After a few passes the collet dropped out of the spindle with no warning and went by me across the shop.  I was lucky.
> 
> Examination showed that the draw bar was two piece with the hex nut fixed to the bar with a solid (tapered?) pin.  The assembly had been blued or surface treated and the ends of the pin were virtually impossible to see without very careful study.  The "slip" I felt was the pin beginning to shear. I immediately turned up a solid draw bar on my trusty Logan 10" lathe.  Don't let this happen to you, that thing could have really hurt!
> 
> I sold the mill-drill in 2000 (Y2K!) and bought a Grizzly knee mill.  This is a step up and at that time the price was right.  It is a 9 X 42 (I think) and the head will rotate but not swivel.  I really like this machine.  Needless to say the first thing I did before I pulled up any tooling in the spindle was to check the draw bar - yes, it is one piece.  Be safe, Geoff



My Micro-Mark mini mill came with a draw bar that engaged about 1/4" of threads on the drill spindle, and only about 3 threads on the collet spindle. After using it for about a week, the bottom most threads on the draw bar broke loose. Fortunately this happened when I was installing the spindle, and not under power.

I went to the hardware store to buy a long 7/16 fine thread bolt, but wasn't able to find one. So I bought an even longer coarse thread one, cut off the threaded portion, and threaded it 7/16-20. Although the new draw bar is only a grade 5 bolt, it engages about 1/2 inch of threads. So far it's working well. Is the bolt strength going to be adequate?

Walt


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## 7HC

Walt said:


> My Micro-Mark mini mill came with a draw bar that engaged about 1/4" of threads on the drill spindle, and only about 3 threads on the collet spindle. After using it for about a week, the bottom most threads on the draw bar broke loose. Fortunately this happened when I was installing the spindle, and not under power.
> 
> I went to the hardware store to buy a long 7/16 fine thread bolt, but wasn't able to find one. So I bought an even longer coarse thread one, cut off the threaded portion, and threaded it 7/16-20. Although the new draw bar is only a grade 5 bolt, it engages about 1/2 inch of threads. So far it's working well. Is the bolt strength going to be adequate?
> 
> Walt



The strength isn't that important as the drawbar doesn't hold the collet in place, the taper does, and the drawbar just has to hold the collet into engagement with the taper.  
The length of thread engagement matters more, as the greater the engagement the more the load is spread over the threads, both when drawing the collet into place and also when tapping on it to break the taper.

I had to make one for my Sieg X1 as the one that came with it is metric and my collets are 3/8-16. 
 I used a length of 'all thread' and welded a coupling nut to the top, then reduced the bottom of the nut to engage with the spindle collar. 

'All thread' is probably grade 5 at best, but I have plenty of thread engagement and there's no distortion of either the drawbar threads or of those in the collets.


M


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## Chucketn

My 2nd hand HF X2 came with scales (minus read out), and a belt drive made by the previous owner. I added a Shumatec DRO-550, the air spring and rack kit from LMS, a larger 2 1/2 hp treadmill motor and controller, and a home brew X axis power feed. The most cost effective was the self assembled DRO-550, and the treadmill motor and controller. Though I did purchase the parts to repair the origional controller, never got around to it. 

Chuck


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## 7HC

Nelson said:


> A question to those of you who own mini-mills.
> Which are the most cost-effective modifications that you can make to a HF or Grizzly Mini-mill?...............
> .......................................Let us know what is on your list of TOP modifications!
> 
> Best,
> 
> Nelson



CNC by a mile!

1: It's a fun project.

2: It removes the tedium of turning handles.

3: You can do machining that is literally impossible to do by hand.

4: It increases the versatility of your machine, i.e. cut out an instrument panel, change to an engraving bit and engrave the instrument panel, put a Sharpie in the chuck and make a poster, change the bit again and make a three dimensional portrait in wood, plastic or metal, add a fourth axis and build a Mars Lander....well, not quite but you get the idea.


M


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## 110octane

I concur that most of the all thread rod is probably in the neighborhood of grade 5.  It seems to be rather "soft" since it is going to be a very ductile because the threads are rolled and not cut.  Today, most all bolts are made by rolling.  The R8 taper is not a self retaining taper because the included angle is too steep.  I think that the all thread should hold the R8 in place.  The connection of the all thread to whatever nut is attached is most likely the weakest point.  Welding undercut should be avoided for example.
I turned the one I used for a replacement from 1018 or 1045, I can't recall.  I used a follower rest to keep the long rod on center.  There are replacement drawbars sold for Bridgeport machines and if, long enough, could be adapted to a mini-mill provided that cost is not prohibitive.
Mainly, just work safe.  In my case it was one of those defects that I failed to notice.  In my defense it was extremely difficult to detect without knowing to look at the assembly.  A bright light, a magnifying glass, and maybe even dye penetrant or mag particle would have been required to identify the defect.
Regards, Geoff Morgan


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## 7HC

110octane said:


> The connection of the all thread to whatever nut is attached is most likely the weakest point.  Welding undercut should be avoided for example.




Agreed, that's why I used an all-thread connector which is really just a very long nut.  Big plug weld at the top of the connector down to the all-thread which is maybe 1/4" from the top, then turn the bottom of the connector in the lathe to a shoulder, which engages with the top of the spindle.
Total cost about $5 and I still have about 2' of all-thread left over.

If the weld failed to properly penetrate the top of the all-thread then the weld might fail when undoing the drawbar and the collet could still be released by tapping the remains of the drawbar with a punch; however it would never fail by being tightened, so there would be no danger of the collet being accidentally released during operation.

Also, I suppose you could harden the last inch or so of the drawbar thread that engages with the collet, but the collets are pretty hard and if either of the threads was to get damaged I'd rather it was on the easily replaced drawbar rather than the collet.


M


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## 110octane

I have a set of Chinese R8 collets and I am not sure as to the method of manufacture.  I suspect the whole unit was carburized to a shallow depth (maybe 0.06" to 0.08") and then ground on the taper and the shank.  The threads do not seem to have been ground after heat treatment.  What is strange is the collets seem to have been made from two pieces.  Looking at the threaded end the top edge of the shank appears to have been rolled over a separate component that holds the threads.  I have a couple of high quality US "Royal" brand R8 collets that are at least to a casual observation to be solid.  I have not had any failures or separation of components with any of these collets, but I'm suspicious.  I have never checked the runout on any of these collets either.  You get what you pay for and in all honesty I have not had any problems with obtaining tolerances at least the ones I have worked to which are not to tenths.
I also have a collection of Chinese, British, and US 5C collets (as well as a few 3AT and 3C which are all US or Italy).  The Chinese collets vary a lot in runout.  The best I can get is within about 0.001" runout with the Chinese collets.  However a number of them can produce a little more than 0.003".  The lesson to this is to check for accuracy before you undertake a close tolerance project.  You might end up blaming yourself when things don't measure up and all the time it was a work holding matter.  I understand that top notch machinists (at least those of the last recent generation) use a new collet and grind the collet in the spindle to assure a precision runout.  I think this was SOP in grinding lathes including grinding the centers anytime the centers were changed.
I don't have to worry about those kind of tolerances.  If I get any less than 0.001" runout in my turning work, I consider it a miracle.  After adjusting the tailstock on my lathe, I have been able to turn between centers, flip the work and get just a "shadow" of lap which I guess represents about 0.0005" T.I.R.which I also consider a matter of luck rather that skill. 
Geoff Morgan


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