Screw On Three Jaw Chuck

D

ddickey

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I plan on buying a cheap screw on 3JC for a rotary table I have. My question is about threads, are they all the same?
 
The adapter is already made. I'll have to check the thread count when I get home.
 
You might consider removing the threaded backing plate and making a new plate for the chuck. There's a potential of unscrewing the chuck from an arbor when cutting on the RT. I messed up a part once using a dividing head with a screw on chuck; didn't remember to do the cutting while only rotating the chuck in a counter-clockwise direction so the cutting forces keep trying to screw the chuck down tighter. You'll see lots of threads on the site where guys warn about running a lathe in reverse with a threaded chuck; risk spinning the chuck off the spindle. The same principle applies to a threaded chuck on a RT. However, I'd guess there are lots of guys who still make it work, just need to be careful. I have a 1 1/2" x 8 tpi chuck for an L&W dividing head that gets carefully used.

On the plus side of making a custom arbor, you might be able to drill/tap a set screw hole in the existing chuck backing plate that has a corresponding tapered hole in the arbor; holes line up with the arbor/chuck are tight.

The thread below is a POTD I did to mount a D1-3 chuck to a backing plate for use on my RT.

Bruce

http://hobby-machinist.com/threads/...in-your-shop-today.14637/page-186#post-355384
 
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