Hello. I have a customer who needs me to cut threads on a pure tungsten rod. I have machined I.D./O.D. on it before, and as usual, sharpen the tool many times, and go slow. But, I need to cut a 1.25-18 thread on the O.D. I have carbide inserts that I have been trying to use, but to no avail. The insert breaks down, and tears the sides of the threads, causing the entire outside edge to tear off, ruining the thread. I have read a few posts around that say the only way to cut a useable thread into pure tungsten is to grind it; and I would really like to single point it if at all possible. I have been told to try some Poly-crystalline diamond coated inserts, however they cost a fortune, and Id love some input from you guys before I buy a $155 insert.
So I guess my question really is....Can you successfully single point a thread into tungsten, or should I stop wasting my time all together? Any help/input at all would be more than appreciated.