Re: [mill_drill] r8 collets
On 04/01/2013 01:19 PM, philr_77378@... wrote:
I don't really understand how the key can help accuracy, once the tool starts spinning, run out is the same, no matter where you locate radially. These spindles and collets The only exception to this I can think of would be if you chucked a piece in the spindle to turn a true cylinder like a lathe, then wanted to remove the chuck & part from the spindle for another operation, and re-install it, but how many people ever do something like that. A simple witness mark before removing the part would do in that case. The only place I can think of where the key might help, is if you have a power drawbar. I have very little time on machines equipped with that, so I don't really remember. There must be purpose for the screw, otherwise why would it always be there, someone out there would know.
On my mill there was a small bump on the taper. The collets I'd been using for 20 years always aligned the say way seem to have conformed to this but a brand new ER-32 chuck that's hardened found it. :(
-- Jerry Durand, Durand Interstellar, Inc. www.interstellar.com tel: +1 408 356-3886, USA toll free: 1 866 356-3886 Skype: jerrydurand
- Hi Folks,
I probably missed it, thought this was the thread about the pin being
long in import mills. The drawbar may be too long, so the threads are
bottoming out before you pull the collet closed. Add a few washers
under the head if this is the case and see if it helps. You can make a
shoulder washer for the top of the spindle for a nicer job.
On 04/02/2013 03:02 AM, John Herrmann wrote:
> Robert -
> I know this is now a relatively old thread, and maybe you've found the solution already. Nevertheless, here's my two cents' worth:
> Given that
> (1) your collets don't close when reefing on the drawbar
> (2) you only see a small amount of taper contact when using dykem
> (3) the collets seem to work OK when you wrap the taper
> I'd say that somebody's (sorry, forgot who first said it) suggestion about the collets being a bit too long has a lot of merit.
> You can check this pretty easily. Pick one of your new collets. Make sure there's no grit or burrs in the slots, and that you can close the slots by hand before putting it into the spindle. Now put the collet in the spindle *without* a mill inside. Tighten the drawbar (fingers should be enough). The gaps in the collet should close up pretty much all the way. If the drawbar seems to "hit bottom" (ie, become hard to rotate) before the collet closes, that's evidence the top of the collet is being stopped from moving upward as far as it should.
> If that's the case, you can try grinding a bit from the top of one collet and repeat the test. If it closes further or all the way, you've verified the problem and the fix. Proceed to grind all of them, and you're good to go!
> - John Herrmann