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Archive for January 16th, 2019

Minilathe MT3 Spindle Collet Fitting

I’ve used the LMS set of inch-size MT3 spindle collets on occasion, but releasing them required an unseemly amount of drawbar battering. It recently occurred to me to check their fit in the spindle taper:

Minilathe - MT3 collet - taper test

Minilathe – MT3 collet – taper test

Huh.

The only place they touch the spindle is right around the base, so it’s no wonder they clamp poorly and release grudgingly. I tried several others with the same result.

Cross-checking shows a much closer fit along the entire length of the dead center, so it’s not the spindle’s fault:

Minilathe - Dead Center - MT3 taper check

Minilathe – Dead Center – MT3 taper check

Stipulated: we’re not talking toolroom precision here

I set the collets on centers:

Minilathe - MT3 collet - drive setup

Minilathe – MT3 collet – drive setup

And proceeded to file away the offending section to move the clamping force closer to the business end of the collet:

Minilathe - MT3 collet - filed result

Minilathe – MT3 collet – filed result

I did the small collets, the ones I’m most likely to need, and left the big ones for another rainy day.

They don’t have much clamping range and seem good only for exact-inch-size rods.

I should lay in a stock of ER16 and maybe ER32 collets for small stuff.

 

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