NYA bench vise

[Illinoyance]

It looks lie the NYA vise is the best of the lot. Machine a new nut and you will have a great vise. I assume the thread is a square thread. You need a boring bar that takes a tool bit at 90*. If you don't have an appropriate bar you can make one from whatever steel you have. The diameter shuld be 3/16 to 1/4" smaller than the bore of the nut. That leaves sufficient clearance to withdraw the tool from the nut. Cross drill it near the end for a 1/4"tool bit. Drill and tap a hole in the end of the bar for a setscrew. Grind the tool to the full width between the threads in the nut. Add proper side and end clearances. The relief an the advancing side of the tool needs to be equal the helix angle of the thread plus 8 to12*. Now you are set up to thread the hole.
Amen on the separate anvil.

 

[silence dogood]

All of you guys have been most helpful. The threads on all three vises measure 7/8" by 4 threads to the inch and they are square thread. I guess that must be pretty standard. I'll fix the duracraft first, since all the pieces are there intact. Since the Craftsman has the same problem as the NYA, I'll use that one as a learning tool before attacking the NYA. The NYA is the keeper.