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Seems like I learn something every time I turn wood. Over the weekend I made a simple cylindrical plinth to stand a trophy on, couple of beads at the top, and a bead and half-cove at the base.

I started with a tenon at the base, finished the top, then reversed the piece holding it in the 8" jumbo plates (Cole Jaws) so I could finish turn and sand the bottom.

It was running true, so I increased the speed to maximum, hoping this would give a nice smooth finish if I took really light cuts. After removing the tenon and making a couple of smoothing passes, I switched off the lathe to check how it was looking ...

WHAT I LEARNED: my lathe's motor and drive shaft stop turning pretty fast -- faster than the inertia of the chuck and jaw plates liked. The whole thing unscrewed from the drive shaft, fortunately friction slowed it down and it dropped gently onto the lathe bed. :eek:

At least it didn't fly across the room, and I was able to fix the workpiece by trimming it down to just a couple of beads at that end.

From here on, when I want to stop the lathe I'll drop the speed to its slowest setting before hitting the power switch.
 

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Duncus,
My cole jaws for my vicmark chuck say 'maximum rpm 800' right on them. Not supposed to spin them that fast. I use them only to finish the bottoms of bowls. Normally just trimming the tenon off and some light sanding. Also take light cuts when using the cole jaws. They aren't meant for heavy cuts.
Mike Hawkins;)
 

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Even spinning fairly slow the big jaws have a lot of momentum. I install the chuck and the put my wrench it and give it an extra push. that locks the chuck on and I haven't had the problem of it coming loose again. I had it happen with a 19" bowl.
I would also not recommend running the jaws at full speed. If something happens it happens faster than you can move. A lady was just killed on a lathe a month ago when a piece blew up. I would imagine a cole jaw would do as much or more damage than a piece of wood. You can get the same quality of cut at a slow speed by simply not pushing the tool as fast. Let the tool do the work.
 

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This has happened to me a couple times, but It happens only because I try to stop the piece from spinning to quickly at the hand-wheel, and only when it is a larger diameter piece.
 

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In the old days, some guys would lose workpieces weighing hundreds of pounds, by the chuck unscrewing from the spindle. Most of those lathes were made good, but the chucks left a lot to be desired. Use of common sense was necessary.;)
 
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