Chuck stuck on Clausing 4900 lathe.

I found the 6" Cushman chuck on the Clausing 4900 lathe that I was re-habing really stuck. I tried using an 18" crescent wrench on one of the chuck jaws to loosen the chuck on the locked spindle, to no avail. I separated the chuck from its back plate, locked the back plate to the ways, made a 2" hex adapter to go on the back end of the spindle and drove that adapter with a 3/4" air impact and 2" socket (the adapter is sitting on the compound in the last picture). No go. I was starting to grind a trepanning tool to machine the back plate off the spindle when my friend suggested trying to use a hole saw instead. That worked really well. After "hole sawing" off the flange, I preceded to turn down the remainder of the back plate until there was about a .02" wall thickness left and the it came of with almost hand pressure.

Follow up post. Does anyone have any leftover threaded back plates with 1 3/4" 8 tpi? I need three. Thanks.

caffeys said:

Follow up post. Does anyone have any leftover threaded back plates with 1 3/4" 8 tpi? I need three. Thanks.

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Grab older US made if you can find them, but if not -

I'm not their biggest fan, ordinarily, but all the Shars CI D1-3 backplates I have purchased so far have been a very good fit.

Their 1 3/4"-8 should be as well.

Thanks for the info. I thought about the Shars option, but until I saw your post I was unsure about the quality of the fit. I measured the spindle threads (I was working on two lathes) with thread wires then made a "dummy" spindle on my old 10ee to use as a test gage. I indicated in the reference surfaces and re-threaded 3 old 1 1/2"-8tpi back plates I had to 1 3/4"-8tpi. Worked well.

If you need more I have used the Shars threaded ones with zero complaints. I made several backplates for my 4914 (when I had it) and they all cut well and had no visible porosity or defects.

I dug the "littlemachineshop catalog out of the burn trash for this, but they offer the 1 3/4-8 backing plate in 6 Inch diameter for $40.

Now, back to the trash with this ;-)