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Use of MT3 collets

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  • Use of MT3 collets

    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?

  • #2
    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.