[GORDYKD]

Drilling with live tool on lathe using holder that has ER25 collet. Keep locking the machine up during drilling. Determined the problem is the drill slipping in the collet and overloading the thrust axis. I know it would be better with a 40 collet but don't have it. Anyone have any tips on improving the torque capabilities on these minimal size collets? Tried using a diamond file to put a little "tooth" on the shank but still slipped. The drill shank is glass smooth so the collet just can't grip it.

[mariojl]

Hi,
While collets are a good help in a machine shop, they tend to slip when you apply a certain amount of torque. When doing milling or drilling, your best bet would be to use either a Weldon holder, which is easy to get and relatively cheap, or hydraulic type holder, or a shrink fit holder.
Mario

[underthetire]

Ya, just try finding a Weldon holder for a live tool lathe...

If your collet is not sprung, and torqued to spec (think its supposed to be about 90lbs on that size, I'd have to check my rigo collet chart) you could put a little lapping compound on it and re try. Not the best solution, but may give it that extra bite.

Edit: 77 pounds

http://www.techniksusa.com/metal/torque_chart.htm