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Thread: Machining tungsten
01-18-2011, 12:34 AM #1
Does anyone on the forum have experience machining tungsten? I have 1/4" pure tungsten electrode material. I need to drill (1/16") hole and turn a point. I am making a hollow electrode. Can this material be turned and drilled using carbide tools/drills ? What coolant or lubricant?
Can the hole be done with EDM?
01-18-2011, 12:50 AM #2
Can't answer myself, but I can point you to the guy who can... jump up to the CNC forum and ask StreetSpeed.
01-18-2011, 01:28 AM #3
Tungsten can be machined with HSS but hard grades of carbide with high rake angles and clearances on the generous side are better, it's abrasive on tools and kind of sticky. Coolant is good but it can be machined dry if the speed is kept down. It machines sort of like cast iron from another planet.
Don't know about EDM, never found a need for it with tungsten, it's not difficult to machine, just different.
I'll never forget the first time a drawing and tungsten were given to me, it was a plasma electrode for NASA in 1964. The stock was 3.00 dia x 7.00 inches long. Tungsten density is very near that of gold and boy howdy that chunk was a surprise to pick up.
01-18-2011, 01:30 AM #4
I haven't machined much personally, but I worked at a shop that did tons of it. The biggest issue is that it is very abrasive. It's also very brittle. Contrary to what your intuition might say, you really need very sharp (meaning uncoated and polished) high positive rake carbide tools, preferably premium micro-grain. You'll just have to add plenty of tooling into your quote. Sharp, high positive rake is important to cut down on chipping by minimizing tool pressure and keeping it concentrated in the cut. I don't remember what cutting fluid they used, but I think it was the standard water soluble stuff they used in most of the other machines. EDM was by far the most preferred way of cutting.
There are lots of other tricks people mention, like heating the tungsten above a certain temperature (can't remember but a few hundred degrees) to get it past the ductile-brittle transition temp., and they tried them all and settled on very sharp, positive rake carbide tooling and lots of it.
01-25-2011, 11:04 PM #5
Thanks for the info. I am making hollow electrodes for an arc device to feed He and carbon into the arc. First attempt at machining with sharpened carbide tool at only 80 RPM gave a very poor result, even when lubricated with a metal cutting compound (Nikx Stikx). A friend suggested some cutting fluid called "Mistic Metal Mover". Worked like a champ - the tungsten cuts like butter. I also used it to drill a 1/16" hole through the electrode with a solid carbide drill bit (1" depth). You just gotta feed slow.