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Power die driver?


Hot Rolled
Oct 20, 2015
I have a part, made from 3/8" 4140 CD bar. It needs a 1.90" long thread, 3/8-24 on one end.
That means I have a 3/8 bar hanging 2" out from support and chatter and push off is a bitch.

These parts get heat treated, and then I have run a thread chaser die over the part after heat treat to ensure they screw into the machine they mount on.

But twisting 350 threads sounds like a bitch.
IS there some kind of die stock that will hold a split die that can be powered on and off in a hand drill or something?

Makes me wish I had a turret lathe and geometric head.

Die HOLDER. Not die stock, not die driver, not power die driver, just DIE HOLDER. I love google.
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Short answer is "yes, there is such a thing." If you want the hollow shank variety to accept the 3/8" thread, the shank OD will probably be at least 1/2". If you want the floating variety with 2" of travel, the device will be somewhat chunky. So, hefty hand drill. But you can also mount them in the tailstock and do them under power on the lathe. If the die holder is not the floating type, unlock the tailstock so it will slide (I am assuming your machine's tailstock is not so massive that it requires rack-and-pinion assist to move).

Various examples here, here, here and here.

BTW, can your part tolerate a small center drill countersink in the threaded end? If so you can probably eliminate your chatter and push off by supporting the free end of the bar with a tailstock center.

[Added in edit] Ah, now I see you posted this in the CNC subforum. You can still use a die holder, but you won't be sliding the tailstock around passively. Your best bet is one of the floating variety, and you will have to arrange a reaction bar to replace the hand-holding these things normally require on a manual lathe. Think of this as a variation of a tension tap holder. Only difference is cutting external rather than internal threads.
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Currently I'm single point cutting them, but the extension from the collet is causing chatter and part deflection.
Of course the other end gets bent before heat treat, so that makes automating the clean up tougher.