Adjusting Nut for Watson 4 Jaw Chuck

[rock_breaker]

I have inherited a Watson Manufacturing CO Toledo, Ohio 4 jaw chuck that has one adjustment nut missing. The chuck is 6" with a 1.5 X 8TPI backing plate. The other adjusting nuts are 0.748" (0.750) X 10 TPI (believed to be Acme) and is 0.868" long, using a 7MM allen wrench. I would appreciate receiving a source where one nut could be purchased if the cost doesn't break the small bank.
Have a good day
Ray

 

[benmychree]

The threads on adjusting screws are generally square threads, not acme. I doubt that you would ever find one, should not be too hard to make one.

 

[ErichKeane]

You can get square-profile threaded rod in that size, but no idea how costly it is (quick google : https://www.uboltit.com/3-4-10-x-3-304-stainless-steel-all-thread-rod.html).

From there, a hacksaw and a rotary broach could handle the rest! If you don't have one, it could be a fun project!

 

[rock_breaker]

Thanks guys!
My slide rule says the pitch angle ? is 5.4` and when I used the a magnifying glass and turning the nut slightly the thread walls appear vertical and parallel on one of the other nuts, Thanks John.
Erich thanks for the source location but got lost in their bid process. If I cant make a nut from my stock of mystery metal I will definitely pursue their pricing.
My real concern is the hex drive as I do not have a rotary broach, may end up forging an allen wrench in a rod then turning to proper OD. Grinding the cutting tool will require some experimentation but I do have several pieces of 1/4" HSS bit stock.
Have a good day
Ray