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View Full Version : Use of MT3 collets



Dunc
04-28-2009, 10:08 PM
Got several of these collets (look like LMS #1948) at a used tool shop. They fit both my minilathe & milling machine and are tapped for a 3/8-16 drawbar.

Most collets that I have seen (in my very limited hsm experience) have a closer or nose cap. These do not.

Is a closer/nose cap an aid to tighten the collet enough to get a secure grip on the workpiece or tool? Or, is it intended to facilitate removal of the workpiece/tool from the Morse taper? Both?

Is a nose cap desirable - even essential?
On the lathe are they acceptable (thinking safety) for operations towards the headstock? Also, towards the tailstock?
On a minimill are they suitable to hold end mills?

If this arrangement is ok, then how hard should I tighten the drawbar? Once operations are completed, how difficult will it be to separate the various pieces given no nose cap?

sch
04-28-2009, 10:43 PM
A closer is superfluous and unnecessary with the MT3 design, which
is similar to Brown and Sharpe in a general way. Removal is by unscrewing
the drawbar by 1-2 turns and giving it a tap or thump with a soft headed
mallet. Then complete the unscrewing of the drawbar to remove the
collet. Lathes are designed for tanged collets in the tail stock, and unless
you modify the tail stock the collet is not likely to hold the work/tool
tightly enough for use. The collet itself locks in place pretty well but the
work/tool will be too loosely held for safety. Headstock use is fine, again
with a drawbar. Hand tightening of a winged nut is usually adequate
torque to lock the work/tool in the collet, but a wrench gives a bit more
to make you comfortable. You do not need to forcefully tighten it.
No lube on the collet though.