Mandrel Question

[TAld]

Back in Nov. there was a discussion on the collet chuck and collets concerning the A&B precision mandrels from Berea. Someone asked how to press the collar stop off. My question is why would you have to press it off? My "A" has 3/4" pass the stop and the "B" 5/8". How far into the collet do you have to go? I measured the inside of the 1/4" collet and it is 3/4" to where it flares out. My 5/16" is on back order from Charles but I would guess it would be about the same. So how far in do you go to be safe from the "wobble demons"?

Tom

 

[Randy_]

Interesting question!! And I don't know the answer; but, out of curiosity, I measured my collets(from 800watt on eBay) and discovered the following. The 1/4" collet(for the "A" mandrel has 0.95" of gripping length and the 5/16" collet(for the "B" mandrel) has has 1.6" of gripping length.

Now for some pure speculation on my part. I'm guessing the er-32 collect are originally designed for use when milling metal and I assume the forces would be much greater in that type of application than in turning pens. That being the case, I would think you would want to use the full gripping length of the collet when working metal; but could probably get away with using less when turning pens.

Since your 1/4" collet has 3/4" of gripping length and your "A" mandrel has 3/4" of length available for gripping, seems like the problem is solved for your "A" mandrel. And since a larger diameter collet will have "MORE" gripping area for a given length, logic would suggest that you could use a little less length on a 5/16" collet.

I am looking forward to hearing from Paul or Bruce or any of our other professional machinists for their insight. Maybe our buddy, Ken, in the far North can offer some light??

 

[Randy_]

Bump.

Sure would like to have some input on this question!!

 

[loglugger]

If you weregoing to turn 1 tube at a time is 1 reason.
Bob