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chuck sticking on spindle

I have a lathe with a 2 1/4" threaded spindle with 6 tpi. It came with a

3-jaw but no 4-jaw chuck. I got an 8-inch 4-jaw off ebay that didn't fit and then a cast iron backplate which had the proper thread. Saturday, I cut down the backplate to fit the chuck and drilled and tapped it to attach.

First time I used it, it got no heavy loading, but I though I was never going to get the chuck back off. Eventually a bunch of hammering on a lever bar broke it free. The 3-jaw has never needed more than a couple hits with a dead-blow hammer, even after I jammed a tool into the work.

Is there anything obvious I should think about to keep it easier to remove? The main interface between the backplate and the spindle seems to be the flat surface on the backplate that is about 3 3/8" in diameter. I never turned that part of the backplate, but I have since polished it with some fine emory and greased it.

Anything obvious I should do beyond what I have already done?

Reply to
xray
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Ooops. That should have been 8 tpi, but it doesn't affect the rest of the question.

Reply to
xray

Clean the threads meticulously, then put a drop of oil on them each time you mount a chuck. The book "How To Run A Lathe" shows how to make a little tool to clean out the internal threads on a chuck backplate. I haven't ever done that, but I use an old toothbrush and occasionally I take my chucks apart and clean everything with solvent, brushes, and compressed air.

If it goes on easily and jams coming off, it may be due to a chip stuck in there is what I'm thinking. The flat area at the back of the backplate is called the "register" and this by rights should be hand-scraped to closely fit. If it's a bad fit and spun on tightly, this could have the effect of jamming the threads and making removal difficult.

Normal chuck removal procedure: chuck a 1' long piece of 2x4 so it sticks sideways out the jaws. Put the lathe in backgear and strike the 2x4 once hard, in the direction to unscrew the lathe. It should free it.

Grant

Reply to
Grant Erwin

Clean the inside of the backing plate with solvent, and then mark it with dy-kem, Hi-Spot blue, or even magic marker. Screw the chuck on and back off, and the place where the dye is removed will show where it is binding.

Jon

Reply to
Jon Elson

Ahhh, good suggestion. Analytical... I like that.

The thread cleaning suggestion is noted and appreciated too.

Reply to
xray

Ahhh, good suggestion. Analytical... I like that.

The thread cleaning suggestion is noted and appreciated too.

Reply to
xray

I keep one of the "extra-huge" blue sharpie pens in the workshop. Almost as good as dye-chem and they don't spill.

He probably has the register diameter a bit short, or a bit small, on the backplate.

Jim

Reply to
jim rozen

All of our hydraulic chucks at work have anti-seize put on the drawtube threads, however they still bolt through to the nosepiece.

Reply to
Steve Walker

Maybe I'm doing it wrong, but I always use the key inserted in one of the sockets. I only need to give either of my chucks a gentle tug to break them loose. I've never had a need to do it, but what if you want to keep a workpiece mounted in the chuck (as in to move it over to a dividing head on a milling machine)?

Reply to
Artemia Salina

Ah. That's when you break out the Ridgid strap wrench! - GWE

Reply to
Grant Erwin

OK, show of hands, who _else_ wants to make the obvious, off-color joke here?

Reply to
Dave Hinz

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