ER32 M3 Collet chuck excessive runout.

S

Stockyj

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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.
 
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.
 
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.
 
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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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.
 
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
 
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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