I am trying to thread a 3/8" diameter Tungsten metal rod on the lathe. I have already killed a WC tipped thread tool. Anyone have any recommendations on the proper tooling for threading this difficult to machine metal?
Machining tungsten is VERY difficult. It work hardens if you look at it crosseyed, and then it gets nearly impossible to deal with. Just drilling a hole in an "easy to machine" tungsten copper alloy requires constant feed. If you hesitate for a second, you're screwed. I've never tried threading it, but it might work best if you can do it in one pass.
Good luck.
Doug White
Grind the threads in with a formed diamond wheel and a toolpost grinder
Bob
If the application of the tungsten rod will allow, Id not thread the rod at all. Id braze on a steel sleeve then cut the thread into the steel. should hold up to a reasonable load.
One of the finest machinists I've ever had the privilege to work with worked for one of my customers - a place that processes refractory metals, including machining tungsten. He told me that he did single point a thread on a pure W rod once, as a stunt. As I recall, he said he had to resharpen a carbide tool after every couple passes. I know that they used to use trichlor for coolant, and the older guys there get kind of misty-eyed when they talk about how great it was for cutting tungsten.
As far as I know, if threads are required in pure tungsten, grinding is the preferred way to cut them.
I'd agree that grinding would be the preferred method, but they can be single pointed. I ran an order of balance screws for one of my customers, years ago. They were made of tungsten and had to be threaded to some non-standard sized 80 pitch thread. I recall that I spent a great deal of time at the grinder, but I managed to turn out the entire lot with care. I'm sure that the fine thread was to my advantage.
I've machined tungsten for other applications as well. It is tough on tools, but machines reasonably well. I'd suggest a C2 grade of carbide, and lots of patience.
Harold
If all else fails, you can buy machinable tungsten alloy rods at
Randal
Thank you everyone for your useful posts. The easiest solution for me is the Steel sleeve-over Tungsten rod, never considered that.
The McMaster-Carr Tungsten costs a small fortune, but a good source for machinable material nevertheless.
-1911
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