Hello, I have a customer looking for some threads on the O.D. of a 99.9% Tungsten bar. Im using a Leadwell LTC-15 CNC lathe, with a Fanuc-OT controller. I am cutting a 1.25x18 thread. I have a KD100 Diamond threading insert. I did a test thread on some hardened 4140 and the thread was sweet, right to size. I put the piece of tungsten in and take my cut. The Root of the thread is sweet, the mating piece feels like it wants to start; BUT the peaks of the thread through out the whole length of the thread just broke right off; and quite frankly I don't feel like I can sell it. Does anybody have any input at all? Ive asked all local machinists and even asked the old guys and they all say you can't machine tungsten at all. Any help would be appreciated. Thanks a lot.