Machining Pure tungsten

I have found a bunch of good info here for various alloys, but not much about pure (99.9%) Is it about the same?

I am quoting a piece...not sure I can do it as it is just about at the capacity of my lathe. Its is big(ish). Its basically a cone with a flange. Flange is about 12" D and has a ton of holes, cone is about 6" tall, thru hole of about 3", otherwise solid tungsten. One surface is 32 RMS, not sure I can achieve that either.

My machine is a manual toolroom lathe and will just swing this at the flange portion.

Any thoughts or advice?

Thanks,

Paul

Call your tool rep. I used a large carbide spade drill to drill through some long rounds in the manual lathe with coolant. The OD of the spade inserts wore significantly. This material is super abrasive on drills. It actually machines nicely but is hard on cutters.

On edit: SAVE THE CHIP$!

I don't know what tungsten sells for, but at about 470# I'll bet thats a pricy blank with significant value in the chips.

Paul hopefully I won't run the thread OT, but out of curiosity what's this piece used for?

BTW Sorry but I can't help the least bit for a solution, NFI how to machine it. I'm going to guess somebody will suggest diamond tipped inserts, but I'm curious to hear the correct answer.

Is this for Allen Wrench?

I could tell you what its for...but I'd have to kill ya! Oddly I have a bunch of diamond inserts, but no tool holder for 'em.

Just looking over the web, I noted that Ferro Tungsten is a popular alloy. One stated advantage of adding iron to the mix is to reduce tungsten's brittle nature. Is tungsten brittle? I have no experience, just curious (so when I build my tungsten-lined muffle furnace, I'll know how to machine the lining).

Pure tungsten is prone to crack when jarred or dropped. When milling it I find it very tough on sharp cornered tools, but with a bull radius (.015) instead of a sharp corner, my tool life typically increases by 3x or more. Does anyone have empirical data on coated carbide cutting tools versus non-coated carbide tools for machining tungsten? When economically feasible we remove larger pieces of tungsten via wire EDM to preserve valuable slugs instead of milling it into chips.

I will clarify my above comment...

Stress cracks propagate dramatically in tungsten. I do not know it to be more prone to crack than any other pure metal. My best experiences with machining pure tungsten have always happened after I first check for cracks by using iron filings and magnet , microscope, or x-ray.

sandiapaul said:

I could tell you what its for...but I'd have to kill ya! Oddly I have a bunch of diamond inserts, but no tool holder for 'em.

Click to expand...

Sounds like you need a new tool holder then

You remember the details (speed/feed, DOC, tooling) on this project?

Tungsten has a brittle to ductile transition temperature of 200 deg C. and higher. The temperature is determined by the manufacturing process and the annealing temperature. The blank may be forged, a electron beam melt, or formed by a powder metallurgy process. The transition temperature is raised by annealing above 1000 deg C.

Drilling is more difficult than turning. The blank needs backup plates for drill entry and exit. A blank heated to above the transition temperature is less likely to crack when drilling.

Use K10 (C-2) carbide for drilling at 150 sfm and .002 in/rev feed. The holes should be no closer than one drill diameter.

Use K01 (C-4) carbide for turning at 130 sfm, .007 to .01 in/rev feed, and .04 to .15 in depth depending on the blank manufacture.

The lathe chuck jaws should have copper shims to prevent part cracking.

A chlorinated cutting oil is used for machining a cold work piece.


Reference Metals Handbook Vol 2 Nonferrous metal properties and Vol 16 Machining Ninth edition

It would be a mistake to bid on this type of work unless you have a opportunity to first verify turning and drilling technique on a practice blank of the same material type and heat treatment.

I use Seco Duratomic inserts about the same F/S as Robert and get a decent life. However,,,,Knurling that stuff sucks.

Someone mentioned above that tungsten is really expensive, which it is, (I had a quote of $18K for 12"x12"x1") but that therefore the chips would be worth something. I have several hundred pounds of tungsten blocks out of radiotherapy linear accelerators and as far as I can tell, there is no recycling market for it anywhere. I think I've asked this before but if anyone knows anywhere to recycle it, please post.