# ER32 M3 Collet chuck excessive runout.



## Stockyj (Oct 14, 2020)

Bought a set of collets and chuck for my lathe but have found the runout of chuck taper is 0.04mm and when you mount a collet with material the runout increases to 0.09mm so that's useless. my 3 jaw chuck is only 0.02mm.
Has anyone successfully ground the taper true, was thinking I could mount my air grinder on tool post clock up the angle and use the top slide to grind it.
Any thoughts.  I have exceeded my refund on eBay due to Covid delays it testing my purchase.


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## mikey (Oct 14, 2020)

Where is the run out coming from? Is it the spindle taper, the chuck, the collets or the collet nut? You need to sort this out before you can make a call.


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## Stockyj (Oct 14, 2020)

The spindle taper is spot on the collet chuck taper is 0.04mm and clamped pin is 0.09mm









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						VID_20201014_140048.mp4
					






					drive.google.com


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## Tozguy (Oct 14, 2020)

mikey will be back to follow up but I just want to say that yes the chuck taper can be trued up easily on your lathe.

But before doing any cutting a thorough diagnosis as mikey mentioned should be performed.


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## Stockyj (Oct 14, 2020)

Is it best to true with a grinder or carbide tip


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## mickri (Oct 14, 2020)

When you have material in the collet does the material go all the way through the collet.  If it doesn't the collet can deform as you tighten the collet nut.  Another thing to check out.


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## Tozguy (Oct 14, 2020)

To skim the chuck taper my first choice would be a very sharp HSS-Co boring tool with generous relief.
If runout is .04mm (=.0015'') then theoretically it only takes a .00075'' cut to true it.

it might be a good idea, while in the same set up, to pick up the external threads and skim those too. For this preferably I would turn the lathe spindle manually with a crank

Before removing the ER chuck from the lathe put an index mark on it so you can put it back always in the same position in the spindle taper.


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## pontiac428 (Oct 14, 2020)

I wouldn't grind it until I was sure I "tapped-tru" the chuck and backplate (if equipped) into alignment as best as possible before grinding.  Do all of your measurement with a ground cylinder or pin in the jaws.  You are close.  Unless your register is a tight fit, I bet you can find the .045 mm to center that way.


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## higgite (Oct 14, 2020)

There is no backplate, guys. The videos in post #3 show it to be a Morse taper chuck.

Stockyj, are you sure both the spindle taper and the MT shank are clean and burr free? Have you tried mounting it at different clock positions? Theoretically, clock positions should make no difference with a Morse taper, but theory doesn't always play out in practice.

Tom


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## mikey (Oct 14, 2020)

You have a lot of interfaces in your set up - the spindle Morse taper, the chuck Morse taper, the chuck's internal taper, the collet external taper, the nut and the test rod. Add to that the need for adequate torque on the nut before you can check run out on the rod. This is collectively called stacking tolerances but each of these can contribute some/most/all of the run out and you need to nail down exactly which it is or what each one contributes in order to figure out what to do about it. I would not grind/bore anything until you do this. As Tozguy said, make a diagnosis first.

I can tell you that a cheap collet can add 0.0007" of run out all by itself. A cheap Chinese nut can double that. This all matters if you are doing second operations work and need precision. For first operations work, it matters very little.


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## Stockyj (Oct 14, 2020)

Tozguy said:


> To skim the chuck taper my first choice would be a very sharp HSS-Co boring tool with generous relief.
> If runout is .04mm (=.0015'') then theoretically it only takes a .00075'' cut to true it.
> 
> it might be a good idea, while in the same set up, to pick up the external threads and skim those too. For this preferably I would turn the lathe spindle manually with a crank
> ...


You cannot cut the Hardened steel with a HSS tool that is definite.


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## Stockyj (Oct 14, 2020)

mikey said:


> You have a lot of interfaces in your set up - the spindle Morse taper, the chuck Morse taper, the chuck's internal taper, the collet external taper, the nut and the test rod. Add to that the need for adequate torque on the nut before you can check run out on the rod. This is collectively called stacking tolerances but each of these can contribute some/most/all of the run out and you need to nail down exactly which it is or what each one contributes in order to figure out what to do about it. I would not grind/bore anything until you do this. As Tozguy said, make a diagnosis first.
> 
> I can tell you that a cheap collet can add 0.0007" of run out all by itself. A cheap Chinese nut can double that. This all matters if you are doing second operations work and need precision. For first operations work, it matters very little.


All was tight all was clean all was repeatable, I have asked for a return thats a long shot if no return I will grind it useless as is.


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## Mitch Alsup (Oct 14, 2020)

Any reason you cannot chuck up an end mill in a collet and check for run out on a surface gauge,
and then use that data to mill the faces true and square ?


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## mikey (Oct 15, 2020)

Stockyj said:


> All was tight all was clean all was repeatable ...



And yet something is off. But as you say, return it. Maybe the next one will be dead on accurate.


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## mksj (Oct 15, 2020)

How do you know it is the ER taper is off vs. the mt end, have you tried to clock the chuck in the MT taper at say 90 degree increments to see if the TIR changes? The additional run-out with the pin could be because of skewing, poor collets or as you say poorly ground. I would also check the +/- readings along a bar out to say 4" to determine skew vs. off center. Problem is if you recut/regrind the taper the nut will still clamp off center then. Not sure to what level these are hardened, put when I make my ER chucks I use a set-tru design and cut the ER taper and nut threads on the lathe so it all runs true.


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## Stockyj (Oct 15, 2020)

The latest is I received a full refund very happy with that. Today I made a holder for my Air grinder will try and grind it true tomorrow will report on the outcome.


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## Lo-Fi (Oct 15, 2020)

I had much more success with a quality carbide tool fixing the taper on my (15 thou runout) Bridgeport spindle than with the die grinder. The grinder tended to simply "follow" the runout no matter how gentle I thought I was being. 

While not particularly hard, the Bridgeport spindle destroyed HSS very quickly. Carbide left a gorgeous finish. I'd expect the same from a collet holder.


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## Stockyj (Oct 15, 2020)

Thanks for your reply I had thought of using a carbide I do have a very good Boring bar and quality tip.  did suspect that the grinder will only follow the runout as the cut is so fine. With a 0.04mm runout, how much cut do you recommend a light or go under the runnout.


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## higgite (Oct 15, 2020)

Before I’d grind on it, I’d do what I mentioned in post #9 and mksj suggested in #15, that is, test it at different clock positions in the spindle. But, I would take it a step further. Not only check TIR at each position, but also mark the high and low spots to see if they follow the repositioning or stay at the same spindle position. This will tell you for sure whether the problem is with the chuck or your spindle bore. The spindle bore can be dead nuts zero runout at the mouth but still be skewed. Just a suggestion. At best, it’ll verify that your spindle is okay. At worst, it’ll indicate that that the spindle is the culprit. Either way, I’ll sleep better at night just knowing.   

Tom


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## mksj (Oct 15, 2020)

I would setup the angle with a sensitive test indicator, use a boring bar, choke up on it so it is as short as possible to minimize flex. You maay also want to ink up the taper and mount up a collet with a rod in it to see if there are high spots or the taper is off.  With the boring bar make sure the tip of the insert is at the center-line of the spindle.  Ideally for shallow cuts in steel I use a sharp ground edge insert with a positive edge geometry, something like a CCGT 32.51 type which is typically used in aluminum. A molded insert or negative rake will not cut the metal in a shallow cut, wit a low feed. I then use a very fine sandpaper to polish the taper and remove any ridges.


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## Stockyj (Oct 15, 2020)

The end result was I managed to find the sweet spot for the Collet Chuck in the lathe spindle and got the runout down to 0.02mm so was no point trying to improve that. But when I mount the collets they don't run true some are better than others up to 0.08mm runout.
I put the (PC) Chinese 3 jaw chuck back on made it true on the backplate and got under 0.02mm (got to be happy with that) so I am back to the chuck and the collet set will stay in the draw for ballast. 
Moral of the story I guess if you buy a $60AU collet set don't expect it to be any good I was very lucky to get a refund.
Thanks for all the replies, I did score a grinder holder out of the exercise as I made one.


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## pontiac428 (Oct 16, 2020)

What kind of collet nut are you using?  I switched to ball bearing collet nuts and saw a strong improvement in concentricity.  If you take a close look at how a collet is loaded under a tightening collet nut, the cause of misalignment and the cure should both become obvious.


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