# How much is too much mini lathe spindle run out?



## WobblyHand (Jan 28, 2021)

Understood that one would like a very small number.

Background - bought an ER32 chuck mounted on a plate from LMS.  I've rotated it several times (only have 3 possibilities due to the holes) and the best TIR on a ground rod is 0.0021".  (Rotating by hand, at far end of spindle.)  I thought it would be better.  Of course the TIR can come from many causes.  If I understand correctly, some of the causes might be:

The 3/8" rod isn't round
The 3/8" collet isn't true
The ER32 chuck assembly is machined incorrectly
The spindle plate locating feature is machined incorrectly
The spindle has run out
Are there other causes?  Have I over simplified this?  While rotating the spindle by hand I noticed if I push or pull the far end of the spindle (at the gear end) I measure 0.001" difference at the chuck end.  (Radial push, not axial.)  Is this too much run out?  Is there an adjustment  to reduce this?  Increase the pre-load on the bearing?  I've never adjusted the bearing so it wouldn't surprise me if it needed tweaking.

Any guidance?  These are garden variety ER32 collets but they shouldn't be this far off, that is if they actually meet their spec.

I have to say, even with 2 thousandths run out, the collet chuck is very nice to use.


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## cathead (Jan 28, 2021)

Maybe put the ER 32 chuck in a four jaw chuck and zero it out.


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## macardoso (Jan 28, 2021)

WobblyHand said:


> Understood that one would like a very small number.
> 
> Background - bought an ER32 chuck mounted on a plate from LMS.  I've rotated it several times (only have 3 possibilities due to the holes) and the best TIR on a ground rod is 0.0021".  (Rotating by hand, at far end of spindle.)  I thought it would be better.  Of course the TIR can come from many causes.  If I understand correctly, some of the causes might be:
> 
> ...



I have a bigger lathe (12x36) so I'm not sure how my numbers should compare to yours. My spindle endplay is about 0.0001 with roughly 20lbf applied to the spindle. Place your indicator on the headstock near the spindle so your pushing doesn't deform the lathe and affect the measurement. My spindle has 0.0002" TIR as measured on the spindle MT5 taper.

My 3 jaw chuck has 0.0035" TIR in the 1" clamping position, it is pretty true in parallelism.

My 4 jaw chuck can be dialed into near zero runout, but suffers from roughly 0.0012"/12" of out of parallelism to the spindle, an issue for longer parts.

My experience with ER systems has been all ER20 stuff. The chuck should be well ground. You can measure chuck runout by dropping a dial test indicator inside the taper. I'd expect you should be able to fiddle with the backplate to get this within a few tenths. Collets make a huge difference. I have purchased China collets with >0.003" TIR (horrible!). Now I only buy Techniks ER collets. They're not too expensive for the quality and they are guaranteed to 0.0004" TIR, which is about as good as you get in an ER system without going to ultra precision single size collets (has zero collapse range, usually only used for tool holding). The collet nut also plays a very significant role in clamping accuracy. For your chuck, I'd invest in a bearing nut, or a Techniks PowerCOAT nut which will have better clamping force and provide better concentricity.


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## WobblyHand (Jan 28, 2021)

I've partially mislead people.  CRS.  The real amount of spindle play is 0.002" on a static spindle.  Just went down and measured it again.  If I push and pull the gear end of the spindle in the horizontal plane, I measure 0.002 play in the horizontal plane at the rod end.  (The gear end is opposite end of spindle from chuck.)  This is as much as the TIR.  Does this point to the spindle bearing being the dominant issue?


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## macardoso (Jan 28, 2021)

In all, I think you need to adjust the spindle endplay. Get that as tight as you can without creating bearing heat. Your lathe manual should describe the adjustment procedure. 0.002" is too loose.

EDIT: Spindle endplay is *axial play*. Once that is minimized, measure *radial* runout. If your indicator is mounted to the carriage, then you have a ton of flexibility of the spindle to the headstock, headstock to bed, bed to carriage, carriage to crossslide, etc. which will throw your measurements off.

Then check your ER chuck without a collet or test bar, get it running true.

Finally buy high quality collets, the cheap ones just do not cut it.


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## WobblyHand (Jan 28, 2021)

macardoso said:


> I have a bigger lathe (12x36) so I'm not sure how my numbers should compare to yours. My spindle endplay is about 0.0001 with roughly 20lbf applied to the spindle. Place your indicator on the headstock near the spindle so your pushing doesn't deform the lathe and affect the measurement. My spindle has 0.0002" TIR as measured on the spindle MT5 taper.
> 
> My 3 jaw chuck has 0.0035" TIR in the 1" clamping position, it is pretty true in parallelism.
> 
> ...


Very good idea on mounting indicator to headstock!  I will do that and report back.

I know about the Techniks collets.  Was too cheap to buy them, but I've stared at them a while.  

At the moment I'm doubting the spindle.  If the spindle isn't true, it's hard to get the rest right.


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## macardoso (Jan 28, 2021)

WobblyHand said:


> Very good idea on mounting indicator to headstock!  I will do that and report back.
> 
> I know about the Techniks collets.  Was too cheap to buy them, but I've stared at them a while.
> 
> At the moment I'm doubting the spindle.  If the spindle isn't true, it's hard to get the rest right.



Yeah, I feel the same pain as you. I settled on ER20 for my mill toolholding and have 24 ER20 chucks. The chucks were $20 each and I have to add a bunch of collets on top of them. Hence why I bought import ones. Unfortunately, the money I spent was just wasted since they were so bad. I can't use most of them and I could have gotten 5-6 really nice collets for the amount I spent. 

You have to get the spindle true first, then deal with the chuck and backplate. Only after those are good can you go to the collets.


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## macardoso (Jan 28, 2021)

One more thought. ER collets center best when properly torqued to spec. This torque is wayyyyy more than you'd expect. For an ER32 collet using a standard (non-bearing nut) you need to torque to 100 ft-lbs. I doubt many of us actually do that, but it does improve TIR when using good collets and nuts. My cheap collets deform under much less torque while the Techniks stay true.


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## WobblyHand (Jan 28, 2021)

macardoso said:


> Yeah, I feel the same pain as you. I settled on ER20 for my mill toolholding and have 24 ER20 chucks. The chucks were $20 each and I have to add a bunch of collets on top of them. Hence why I bought import ones. Unfortunately, the money I spent was just wasted since they were so bad. I can't use most of them and I could have gotten 5-6 really nice collets for the amount I spent.
> 
> You have to get the spindle true first, then deal with the chuck and backplate. Only after those are good can you go to the collets.


Well, once you measure things t_he right way_, things do not look so bad.  Dial indicator on headstock.  Measure spindle runout at chuck taper.  A tiny fraction of a tenth.  (Less than a 10th of a 10th.) Let's call that good!    With the cheap collet in place and a rod of unknown provenance about 0.0009".  Guess the chuck is fine.  Maybe not the collets or rod.  I can figure that out later.  At least it's very fixable.

Pushing or pulling the spindle at the gear end in the horizontal or vertical plane resulted in no discernible movement at the chuck taper surface.

That was a lesson in metrology... Don't indicate off the compound!  It's too wiggly!  @macardoso thank you so much!

Now to get things a little more rigid.  Tough with what I have, but maybe there are some improvements to be made.  Different thread.


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## macardoso (Jan 28, 2021)

It is amazing how much machines move under load - even really big ones. Usually the best you can do is understand how it moves and compensate with spring passes or other techniques. Think about how hard you pushed on the machine and then compare with the force of actually cutting. That's why people with smaller machines struggle to hold tolerances which are pretty easy to hit on heavier machines.

Another important point, and not to be understated, is the fit and finish of the mating components (bolt flanges, ways, gibs, etc.) play a huge role in machine rigidity. You usually can't do much about the amount of iron you have to work with, but small improvements in the fit of the machine components can have huge increases in rigidity and accuracy.


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## WobblyHand (Jan 28, 2021)

macardoso said:


> One more thought. ER collets center best when properly torqued to spec. This torque is wayyyyy more than you'd expect. For an ER32 collet using a standard (non-bearing nut) you need to torque to 100 ft-lbs. I doubt many of us actually do that, but it does improve TIR when using good collets and nuts. My cheap collets deform under much less torque while the Techniks stay true.


That's good to know.  I torqued it down, but not that much!  Might have only been 20 ft-lbs.  The ER32 spanner wrench I have is short and I haven't even made a tommybar to fit the chuck yet.  I was using a hex key as the tommybar.  Now that I know the chuck is ok, I'll make a bar.


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## macardoso (Jan 28, 2021)

WobblyHand said:


> That's good to know.  I torqued it down, but not that much!  Might have only been 20 ft-lbs.  The wrench I have is short and I haven't even made a tommybar to fit the chuck yet.  I was using a hex key as the tommybar.  Now that I know the chuck is ok, I'll make a bar.



You *probably* don't need to get it that tight but just making you aware that these do come with a manufacturer recommended torque.


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## WobblyHand (Jan 28, 2021)

Seriously, 100 ft-lbs is a lot of torque!  Yes I could do it with my weight, but one has to be in the perfect position to do this.  I wouldn't be able to do this in my current setup.  I'd have to make some long bars and a long wrench, at least 12" long each.  @12" I'd need 100 lbs of force.  Doubling the distance would halve the force.  That would be a crazy ER32 spindle wrench to be sure!  

My takeaway from this is to tighten the collet a lot tighter than you thought you should have.


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## Mitch Alsup (Jan 28, 2021)

I am going to suggest something that some might consider sacrelige........

If you wan tthe ER chuck to run true, you are going to need to machine some clearance on it (whatever is preventing it from moving wrt spindle)
and then tap it into true as you torque the bolts holding it to the spindle.

Sort of like traming a vise on a milling table, but in rotation instead.


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## WobblyHand (Jan 28, 2021)

Mitch Alsup said:


> I am going to suggest something that some might consider sacrelige........
> 
> If you wan tthe ER chuck to run true, you are going to need to machine some clearance on it (whatever is preventing it from moving wrt spindle)
> and then tap it into true as you torque the bolts holding it to the spindle.
> ...


I thought I might have to do that, but was really hoping it wouldn't be necessary.

I don't know yet the repeatability of the chuck TIR.  By that I mean remove the chuck assembly, remount on the spindle and measure the TIR. At the moment, I'm just amazed at ~0.00001" runout.  1/10th of a tenth.  So I'm not anxious to remove it today.  (I'll move it, but not today!)  I have the location marked, but it's only a sharpy, which can be easily rubbed off.  When I'm a little more sure the location is a keeper, I'll punch the location to mark the assembly plate.  That way I won't have to guess each time.


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## macardoso (Jan 28, 2021)

WobblyHand said:


> I thought I might have to do that, but was really hoping it wouldn't be necessary.
> 
> I don't know yet the repeatability of the chuck TIR.  By that I mean remove the chuck assembly, remount on the spindle and measure the TIR. At the moment, I'm just amazed at ~0.00001" runout.  1/10th of a tenth.  So I'm not anxious to remove it today.  (I'll move it, but not today!)  I have the location marked, but it's only a sharpy, which can be easily rubbed off.  When I'm a little more sure the location is a keeper, I'll punch the location to mark the assembly plate.  That way I won't have to guess each time.



Not trying to be mean, but let's double check that TIR. How are you measuring it and can we verify the indicator is not bottomed out? That kind of runout would put you in the ultra precision class of lathes seen only in laboratories.


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## WobblyHand (Jan 28, 2021)

Not bottomed out, I checked for that.  However, I could very well have made a mistake!  And I'm not afraid to admit mistakes. Witness this thread.  

I have a Noga indicator holder.  It is magnetically attached to the top of the headstock.  (Not the cover to the headstock.)  I have a Federal 0.0001" dial indicator.  (The dial indicator was my Dad's, when he worked as a technician at the MIT Radiation Laboratory just after WWII.  He helped build their cyclotron among many other things.)  I have positioned the dial indicator so that it touches the taper of the chuck near but not on the edge of the taper.  I adjusted the indicator so that it pushed in by about 0.005".  (So I can easily tell if I "fell off the indicator")  Rotated the dial face to read 0.  Grabbing gear end of spindle, rotate the spindle by hand 360 degrees.  Measure difference between minimum and maximum setting.  Rotate a few more times, just to see if the measurement effectively repeats.

I'll measure it again, since it does seem _too_ good.  Next post with a picture of the set up and measured results.


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## Lo-Fi (Jan 28, 2021)

WobblyHand said:


> I've partially mislead people.  CRS.  The real amount of spindle play is 0.002" on a static spindle.  Just went down and measured it again.  If I push and pull the gear end of the spindle in the horizontal plane, I measure 0.002 play in the horizontal plane at the rod end.  (The gear end is opposite end of spindle from chuck.)  This is as much as the TIR.  Does this point to the spindle bearing being the dominant issue?


I've no idea what brand of mini lathe you have, but I know a mate of mine replaced his spindle bearings in his mini lathe with branded ones - nothing expensive, fancy or precision - and it transformed the machine. He had 0.005" static play before and around 0.0002" after. I'd bet that $15 worth of bearings will probably do similar for you.


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## WobblyHand (Jan 28, 2021)

I'm not discounting the bearings yet.  Need to go downstairs and measure stuff again.


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## macardoso (Jan 28, 2021)

If you do have that good of runout, good for you. I'm jealous!


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## WobblyHand (Jan 28, 2021)

Ok, did it again.  The dial indicator had a little stiction, and would drag a little at the start of rotation.  I added a drop of oil to the surface and remeasured.  The oil helps.  So it's not 0.00001".  It's just under 0.0001".  Wish the Noga was slightly bigger (in this case) but I was able to take the measurement.




Even though it looks like it, the body of the indicator is not touching the chuck.  As you can see, (third picture) the indicator is pushed in 0.010".  (1|0 line)  When it's at full extension, the small indicator is on the 0|9 line.   When I rotate the chuck 360 degrees, the big needle only varies between two minor divisions, which is under 0.0001".  

I have a DTI, but it only has 0.0005" marks.  It sure would be easier to use, however.  I might have cosine error with the dial indicator, as I'm not normal to the surface.  If I extended the plunger on the dial indicator, maybe I could get closer to normal.

But this second measurement seems to tell me, stuff isn't too bad.  Not sure about fixturing repeatability, but at least this measurement is ok.  Comments?  Did I do this right?  What would you do different?  (Besides not buying a mini lathe...)


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## macardoso (Jan 28, 2021)

WobblyHand said:


> Ok, did it again.  The dial indicator had a little stiction, and would drag a little at the start of rotation.  I added a drop of oil to the surface and remeasured.  The oil helps.  So it's not 0.00001".  It's just under 0.0001".  Wish the Noga was slightly bigger (in this case) but I was able to take the measurement.
> View attachment 353039
> View attachment 353040
> View attachment 353041
> ...



I mean, dang, thats awesome.


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## macardoso (Jan 28, 2021)

The best method would be to use a 0.0001" Dial test indicator and test at 3 locations along the taper (lip, center, bottom). This would verify radial and angular runout and well as taper form if you indicated the traverse direction as well, but your method is plenty good for the home shop.

I'd be extremely happy with that, and probably would never remove that chuck until the end of days


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## mikey (Jan 28, 2021)

I have a couple of comments that may or may not be of any use:

A dial indicator is the wrong tool to use for this kind of measurement. Even a 0.0005" DTI would be better. You not only have cosine errors but are adding in hysteresis in the indicator when used in this fashion.
An articulating arm indicator holder can flex excessively, especially when extended out as you're doing. It makes accurate readings very difficult. I've been measuring concentricity on lathes for a very long time and know that measuring from the cross slide with a solid indicator holder is more than solid enough to overcome the spring tension of a DTI. If you must use that holder then use the right kind of indicator and choke up on the extension to the bare minimum.
Can you tell us what your spindle run out is? I mean when measured properly with the right set up? This has nothing to do with the chuck evaluation; mostly, I'm just curious.
This is just an opinion but while using good collets and nuts are critical on the mill, the same is not necessarily true on the lathe unless you are doing ultra-precision work to very, very tight tolerances. Because of the wide range of work piece diameters, collets get compressed with regularity and that will affect their long term accuracy so using ultra-precision collets in a lathe collet chuck may not be the wisest choice. My personal approach is to use a good nut and import collets on my lathe and this has been accurate enough for the work I do.


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## WobblyHand (Jan 28, 2021)

Yes, I'm reluctant to take it apart!  

Too bad the rest of the lathe is a bit wiggly.  Going to have to figure out how to clean up the dovetails and gibs.  It's a bit over my head, at the moment.  I've adjusted the gibs everywhere, but that isn't seemingly enough.  Somethings not flat, or there's some bolt head with an issue, or who knows what.

@mikey, this is why I posted the pictures.  Words only get you so far.  Previously I had mounted the dial indicator on the QCTP and saw terrible runout at a chucked rod.  @macardoso suggested attaching the indicator to the headstock to eliminate QCTP/compound/cross-slide issues.  The arrangement I used for the dial indicator measurement posted above is awkward at best.  It's extended way out, and it was difficult to get it to stay in position.  Also the angle of the dial indicator.  That's why I mentioned cosine error.  I will try your suggestion of a DTI on the cross slide.

As for spindle runout, (either radial or axial) I've never measured it directly.  But I suppose I can measure it now, after I measure the collet chuck.  The reason I even thought about it because it can limit one's TIR.  Bad spindles make it hard to have low runout.  Originally, I was just checking if the collet chuck was good, or if I had to return it.  That's why I started this whole thread - apparently because I don't know how to measure this stuff very well yet.  

My ER32 collets are a cheap set.  I remembered your writing about that.  I'm not hoping for ultra precision here, just good enough so that >98% of the time, if it fits in the collet, I don't even have to think about it.


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## mikey (Jan 28, 2021)

WobblyHand said:


> Yes, I'm reluctant to take it apart!
> 
> Too bad the rest of the lathe is a bit wiggly.  Going to have to figure out how to clean up the dovetails and gibs.  It's a bit over my head, at the moment.  I've adjusted the gibs everywhere, but that isn't seemingly enough.  Somethings not flat, or there's some bolt head with an issue, or who knows what.
> 
> ...



I think I have 6 or 7 Noga indicator holders and several from Mitutoyo. Of all of them, the two-arm Noga PH2040 is the most quick to use and rigid and I really like them, so much so that I recently ordered a second one as a back up. If you're interested, here it is on Amazon. I much prefer this holder to check run out on machine spindles and chucks because it will not move. Lock the magnet on the cross slide, choke up on the extension and you will have as rigid a set up as I've seen. And this matters because we're measuring run out in the tenths so even a tiny bit of flexion in your set up makes a difference in the readings. 

I discussed checking the spindle run out in another thread in the past. Maybe review it to refresh you thoughts on the subject because I agree with you that you really need to know your spindle's baseline readings. I also agree that checking your chuck's run out is an important bit of information. I did the same thing and it helped me decide to keep it. 

Use your cheap collets on the lathe and save your money for good collets for the mill. I found that a good nut can reduce run out significantly, even with import collets. However, don't take my word for it. Check your spindle, then check your chuck, and then use a precision pin and check the run out of your import collets with a good nut and see for yourself. It is educational.


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## WobblyHand (Jan 28, 2021)

Well, for now, I have what I have.  Not that things can't change, but what I have, is what I will measure with.  Put the Noga on the cross-slide and locked the carriage.  Installed my DTI.  On the chuck I got about 0.0013" didn't seem to matter where  I measured, out near the edge, or more inside the taper.  Silly me doesn't like that answer as much.  Since my measurements have gone from 0.004 on the QCTP, to 0.00001 and 0.0001 using the dial indicator, and 0.0013 with the DTI, I'll just leave the measurements as they are.  Before removing the chuck I marked the relative position.

Next I measured the spindle itself.  For the inside bore of the spindle I got, just estimating here, about 0.0001" runout with the DTI.  Then I measured the register which came out at maybe a few tenths larger.  The register was a lot less smooth than the inner bore, so there were some pops, but the runout in the radial dimension is well under 0.0005", probably closer to 0.0002".  I could not make the DTI move more than 0.00005 by really pushing or pulling the gear end of the spindle.  You could tell it slightly moved, but I couldn't measure it at all.



Unfortunately the register surface is interrupted, (you can see it at 2 o'clock on the first picture,) but there really wasn't all that much runout, save for some rough surface edges.  I hope I am using the DTI correctly.  If not, would someone let me know.  For the collet chuck I attempted to make the DTI arm nearly parallel with the taper and only preloaded the DTI by about 0.010", same with the spindle measurements.  I oiled the surfaces to make it smoother sliding.  Trying to reduce friction on the little ball.  Hope that's ok.

I will read the linked thread, just haven't yet as of this posting.

Edit: changed _locked the cross-slide_ to _locked the carriage_


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## WobblyHand (Jan 28, 2021)

I did clean things, but apparently I missed the do not oil admonition.  Not positive that the measurements were as repeatable as @mikey would like, but then again, it's all I have right now.  I have the Noga DG61003 and an ancient Enco 0.0005" DTI.  The Noga is tons better than the POS HF one.


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## mikey (Jan 28, 2021)

Your DTI positioning is fine, as is the indicator holder. As anal as it might seem, these things make a difference.

0.0001" TIR on a spindle is damned good. Actual run out is 0.00005", and on a lathe that is essentially zero. Typically, the spindle register should be very close to the same run out and since there is not much you can do about it anyway, I would accept it for whatever it is.

To most accurately measure the taper of your collet chuck you need to clean everything again, then apply a very light coat of oil in the spindle taper and install the chuck. Take your readings at the inside taper of the chuck near the opening, midway and near the end of the taper. Record all of it, then take the chuck off the spindle, rotate it to the next possible mounting position and repeat your readings, then do it again at the last possible mounting position. This will tell you which mounting position is the most accurate and how much run out you can expect. Place a witness mark on the chuck that is aligned with the witness mark on the spindle and mount it that way every time you use it.


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## WobblyHand (Feb 5, 2021)

To close this out, I was able to find the least TIR position on the  collet chuck, which turned out to be about 0.00075 - 0.0008.  Then I measured the TIR of the same 3/8" rod in a 0.375 ER32 collet.  The runout was just under 0.001".  I'm calling that good.  Especially since I don't really know that the rod is that tightly toleranced.  (And if the collet was as advertised.)  Put a witness mark on the chuck (and spindle).  

This exercise makes me want a better DTI.  It wasn't that easy guesstimating the values.


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