5C Set-Tru Collet Chuck Repeatability

Greetings,

I recently purchased a new Bison 5" 5C Set-Tru collet chuck with an L00 backplate. Took a skim-cut on the face of the back plate to eliminate about .001 of axial runout when mounted on my spindle. The chuck was mounted and zeroed for < a tenth of run out on the inner 5C taper. Mounted a 3/4" test bar in a collet with less than 2 tenths TIR 1" from the nose.

Now my question, after unmounting and remounting the chuck on the spindle I typically measure about .0007 of runout on the 5C taper, worst case about a thou and 2 thou TIR on the test bar. This is good enough for about 80% of the work I do, but not when I need to flip and re-chuck a part.

Is this repeatability typical for this setup? Am I going to need to redial this in every time I mount the chuck and have one of these re-chuck jobs or, is there a possible issue with the taper mount on the spindle or chuck? TIR on my spindle is < a tenth, no burrs, super clean.


Ted

Is your before and after taken with the test bar still in the chuck? If the lathe spindle and the chuck taper are both good, I would think it should repeat better than a tenth, just removing and remounting the chuck. You might want to isolate the potential problem into chuck/spindle and chuck/collet


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ripperj said:

Is your before and after taken with the test bar still in the chuck?

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The before and after on the test bar is 2 tenths before and 1 to 2 thou after, 1 inch from the nose. The before and after on the 5C taper in the nose of the chuck is < 1 tenth before and 5 tenths up to a thou after removing and remounting the chuck on the spindle. I am going to dismount and mount it a few more times to get additional readings. will post results...


If this is the best it repeats I am going to have to dial it in when needed, I don't think I will ever be able to do it as quick as a 4 jaw, have to loosen 3 cap screws locking it to the back plate and then the 4 Set-Tru screws which on the Bison are not spaced 90 degrees each, not sure I understand why they are spaced the way they are.

Maybe I am just being a whiner, thought it would be a bit easier than this...

-Ted

Have that same collet chuck. I just reset as needed. DO NOT loosen the from mounting bolts and you will be fine. It's not necessary, the adjusting screws will move the chuck body.

Hope this helps !

What makes you think it should repeat like that when you mount/demount the chuck? It is supposed to repeat from part to part in the same collet.

tdmidget said:

What makes you think it should repeat like that when you mount/demount the chuck? It is supposed to repeat from part to part in the same collet.

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.002 TIR isn't much better than the 3 jaw, just seemed like it should be better. Once trued in, re-chucking with the same collet is fine ~0.0002 with an import collet. It is a new set up for me, so I did not know what I should expect...

It seems like there is a problem with the seating of the L00 male and female tapers. Does the runout change if you tonk the side of the chuck nose with a dead-blow hammer? I suggest you take off the key, blue up the female taper, and see how it is seating on the make taper. Taking off the key lets you apply a little twist and see the seating better. A L00 taper should repeat dead nuts, but if the angles are mismatched or there are dings and burrs, the assembly can cock one way or the other ever so slightly each time you mount it. Also make sure the threaded L00 ring is not dinged up and pulling one side more than another.


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wr4t said:

Once trued in, re-chucking with the same collet is fine ~0.0002 with an import collet.

Click to expand...

This is good, and what you'd expect.

Success!

rklopp said:

Also make sure the threaded L00 ring is not dinged up and pulling one side more than another.

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Thank you for the tip, the threads on the L00 back plate still had burrs on them. The clamping pressure on the taper from the lock ring must have been uneven. Filed the burrs down and cleaned up the rough looking threads. Repeatability much improved over 5 mounts dismounts:

1. nil
2. < 0.0003
3. 0.0001
4. 0.0001
5. 0.0001


Torqueing the lock ring down every 90 degrees with the spanner was necessary to get better than 0.0005, and the tip about keeping the bolts holding the chuck to the back plate tight when adjusting the Set-Tru cap screws greatly simplifies zeroing in the chuck.


Appreciate the helpful tips,


Ted WR4T

Those readings are about as good as you can expect for the machine and chuck you've got. Glad you solved the issue.