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Pratt Burnerd Multisize Collet Chuck—slipping lever.


May 4, 2023
Heya guys. On my Clausing 6300 I have a PB Multisize collet chuck and I love it. It came with a full set of collets and the runout is near nonexistent. It’s a joy to use.

The issue I am trying to solve is the lever: when the machine starts spinning, it will very slowly disengage. Just slowly slide backwards until it’s unlocked, over the span of say, 30 seconds.

I contacted PB and have scoured the internet looking for some vintage documentation on lever hinge placement. No luck. And as of this morning, I’ve tried 3 or 4 various locations— clamped to the headstock, to the bed, etc— and the end result is still a loose lever.

I’m still not sure if it’s lever hinge placement or if it’s something else at this point. Is there a set screw or something hidden somewhere?! I’ve found the use of this collet chuck to be intuitive—screwing the front in until grip is sufficient once lever is engaged, etc—, so I don’t think it’s user error.

If anyone here has this collet chuck and wouldn’t mind sharing pictures of how they’ve set up the lever hinge, I’d be forever appreciative.

(I will also admit that there are 9 balls around the diameter of this chuck. 1 of those balls may or may not have definitely fallen deep behind the lathe. Ive tried magnets. Can’t reach the darn thing. I’ve noticed no change in performance but figured I’d mention)


Feb 19, 2002
Peralta, NM USA
Doesn't the lever cam over? Maybe I'm misremembering.

As to the balls - they're 19/32, available on ebay for $10 for a pack of 10 (including shipping). If you were local I'd just give you the one I've had on my desk for the past few years. If you've got a set of 15mm balls they'd likely work as well.