mecam:

I have the Rodchuck system and use it to make 4-40 pushrods. The base stock is 1/8" welding rod. The Rodchuck uses a 2 die method. 1st pass is with a 5-40 die which sets the correct thread count then a second pass with the 4-40 that reduces the threaded diameter and gives the correct sizing. Works like a champ.

Any round stock will work. The test is if you can EASILY file a flat on it then it can be used to cut threads.

Dan