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ronald44181000
03-27-2013, 07:03 PM
Does anyone have any idea's as to what type of tooling I need to cut and knurl tungsten rod? I've tried HSS and Carbide tool bits. Carbide shatters and HSS doesn't even make a scratch in it. I've thought of trying Ceramic Cutters, but I'm open to suggestions.

kf1002002
03-27-2013, 07:24 PM
I suggest you make cutting tools of the tungsten. It's hard stuff but diamond might work. From what I've read it's more commonly pressed and sintered from tungsten dust.

Ken

Toolguy
03-27-2013, 07:36 PM
Apparently you are trying to machine Tungsten Carbide. Pure Tungsten is fairly soft and easy to cut.
About the only way to work with Tungsten Carbide is a diamond grinding wheel.

RWO
03-27-2013, 08:31 PM
My old "Machining Fundamentals" book says that pure tungsten can be machined with carbide if you preheat to about 400 deg.F. If so, you could keep a torch played on the backside of the workpiece while cutting with a carbide parting tool. Knurling might be a problem if you cannot find carbide cut knurling tools.

RWO

Evan
03-27-2013, 09:24 PM
Pure tungsten is reasonably easy to machine. Tungsten carbide is not machinable with any common or even uncommon tooling. It is ground to shape with diamond tooling. In most cases tungsten carbide tooling and other shapes are made by hot pressing to either net shape or very close to net shape. Tungsten carbide tooling is made using tungsten powder with cobalt metal as a binder. It is pressed in molds at the fusing temperature of cobalt. When recycled it is heated to the melting point (liquidus) of cobalt which is then spun out of the powder to recover the tungsten for reuse.

tdmidget
03-27-2013, 10:20 PM
This appears to be a good example of using the wrong terminology. Pure Tungsten is virtually useless except for incandescent bulb filaments and vacuum tube electrodes. So every one has to guess what the material actually is.

flylo
03-27-2013, 10:49 PM
I have 100+ pounds of coarse tungten carbide like they use on oil drilling bits. About the size of roof granules. Any idea where to sell it for more than scrap? This is not a offer to sell. It's a want ad for info.

dfw5914
03-27-2013, 11:10 PM
Pure tungsten is sometimes used for ballast blocks on aircraft.
When I was working at a helicopter completion center we would occasionally have to install tungsten ballast blocks.
Usually the ballast would be secured using existing fastener locations, so we would mark the locations and send it over to the machine shop
to be drilled and reduced to the required weight. Never heard any complaints about it being difficult to machine.

john hobdeclipe
03-27-2013, 11:14 PM
Sintered tungsten carbide can also be machined via EDM.

Toolguy
03-27-2013, 11:17 PM
Pure Tungsten is also used for guide rods in semi auto pistols to add weight. It is very dense and heavy.

Optics Curmudgeon
03-27-2013, 11:51 PM
Unless some special characteristic of pure tungsten is needed it makes no sense to fight with the stuff. It's hard and brittle and needs to be ground to final size if finish is important. Fortunately, industry has a solution, W/Ni/Fe alloys, which are nearly as heavy, but quite machinable. Here is an example: http://www.mi-techmetals.com/products_tni.htm. I deal with parts made from this stuff regularly, and have seen it machined.

Duffy
03-28-2013, 12:09 AM
Sintered tungsten metal was used extensively as a shielding material in transfer cases for radioactive isotopes, particularly cobalt 60. Atomic Energy of Canada routinely machined various sizes of spacers from tungsten stock purchased in England. I was told that it machines somehat like cast iron, but I think they used carbide tools. I have one of those spacers, so I might have a go at it tomorrow. Stay tuned.

Evan
03-28-2013, 12:28 AM
Pure tungsten is sometimes used for ballast blocks on aircraft.

It was also used as ballast blocks on the Curiosity Mars Lander/Rover. Just before atmospheric entry it ejected two 165 lb tungsten ballast weights which left craters easily visible from orbit. That unbalanced the landing craft so it would trim it to provide lift in the air. After entry it ejected another six 55 lb blocks to rebalance it. They left more craters.

gearedloco
03-28-2013, 12:47 AM
Which form is used as welding (TIG) electrodes? Whatever it is, it's pretty darn hard.

-bill

ronald44181000
03-28-2013, 08:52 AM
Thank's for the info, I'll be definitely be using your suggestions as well as the link that you provided.
I should have mentioned in my original post that I'll be producing match grade dart's for friends and other client's.

Ian B
03-28-2013, 09:16 AM
Ah, so it may not have been wrong terminology! I had a look, it seems that tungsten dart barrels are usually made from an alloy of tungsten, often W-Ni-Fe, W-Ni-Cu, W-Ni-Cu-Fe. Some of them contain up to 95% of tungsten, and it's not too much a stretch of the imagination to think that pure tungsten rod can be used. This my be what the OP has, and he's just having troubles machining it.

It could also be, of course, that he's got some tungsten carbide rods and *believes* them to be tungsten. From his description of machining them, this could well be the case. Testing for that first would be a good idea - just run a file across the end of one of the rods. If the rod gets smaller, it's tungsten. If the file gets smaller, it's tungsten carbide...

Ian

beanbag
03-28-2013, 09:23 AM
Also pure tungsten is not magnetic and tungsten carbide is slightly magnetic.
Tungsten will not scratch HSS, but tungsten carbide will.

Ian B
03-28-2013, 10:06 AM
If it *does* turn out to be tungsten or one of its alloys, here's a bit about machining it: http://www.edfagan.com/litPDF/Machining_Guide_Tungsten_Alloys.pdf

(but my money is on it being tungsten carbide...)

Ian

Weekend_Scientist
03-28-2013, 10:25 AM
Uhh Guys,


"Pure Tungsten" as in metallic tungsten (NOT carbide) isn't always as "soft" as the text books would have you believe. If your metallic tungsten isn't quite as pure as you would like and it has just a bit of oxygen in it it gets hard and brittle fast.

A good example of this is tig electrodes, at least the lower grade ones are quite brittle and they are metallic tungsten not tungsten carbide.

Heating tungsten in an oxygen atmosphere causes oxygen to diffuse into the tungsten and make it more brittle. I'm not sure if the aforementioned 400 degree F pre-heat is enough to cause a problem but when it gets hot enough to glow it gets brittle fast.

beanbag
03-28-2013, 11:13 AM
U but when it gets hot enough to glow it gets brittle fast.

That's the opposite of my experience. I used to bend tungsten rods by heating them.

1-800miner
03-28-2013, 11:32 AM
I have worked in several tungsten mines. That is the hardest stuff to drill.
Drilling a tunnel round in granite you will two or three carbide bits.
Same round in tungsten rock? Take a dozen bits and you might get it all drilled.

That rock sure is pretty when you shine a black light on it.
Looks like you are seeing all the stars in the night sky.

Weekend_Scientist
03-28-2013, 11:34 AM
Sorry, I should have been more clear.

Heat it up to incandescence...then...let it cool back down to room temperature. Now you've got tungsten metal with a lot of gasses dissolved into it and it is more brittle at room temperature than it would have been if it had never been heated in the first place.

I'm sure other metals act similarly but tungsten seems to be particularly bad after it has been heated (and cooled) in atmosphere.

RWO
03-28-2013, 02:14 PM
Mcmaster-Carr sells a sintered tungsten-nickel-copper alloy that machines easily.
http://www.mcmaster.com/#tungsten-rods/=m2rn0t

They also have this to say about tungsten properties;

http://www.mcmaster.com/#8788aac/=m2rpcy

RWO

Duffy
03-28-2013, 07:53 PM
I chucked up my tungsten spacer block and tried machining it. It center-drilled with difficulty using a hss center drill, but a carbide drill marched through it. A new, but cheap, brazed carbide turning/facing tool had absolutely no problem facing the 1 1/4 diameter spacer using top speed on my old Logan. It was a bit dirty though.

koda2
03-29-2013, 01:23 AM
A bit of thread drift here, but tungsten has come to be the standard bucking bar for light aircraft rivets.
Very dense, fits in small spaces.
http://www.tungsten-bucking-bar.com/about_us.html

Dave A.

derekm
03-29-2013, 07:43 PM
tungsten is used in ultra vacuum systems as a pump using its ability to "get" gas molecules.

beanbag
03-29-2013, 07:52 PM
tungsten is used in ultra vacuum systems as a pump using its ability to "get" gas molecules.

No, that would be titanium.

Tony Lippmann
12-22-2013, 08:30 AM
I have been trying to machine 95% Tungsten W-Ni-Fe with no success so far.
Turning is OK, but when it comes to drilling & tapping it becomes a real problem.
I have had some special taps made and even made the tapping hole 4.5mm dia instead of 4.00 yet still the tap just skids off the surface.
I will also have to drill & ream this material.

Can anyone please help.

Tony

macona
12-22-2013, 11:22 AM
I have 100+ pounds of coarse tungten carbide like they use on oil drilling bits. About the size of roof granules. Any idea where to sell it for more than scrap? This is not a offer to sell. It's a want ad for info.

Tungsten carbide with no steel attached is about $9 a pound around here.

jhe.1973
12-22-2013, 02:00 PM
Heat it up to incandescence...then...let it cool back down to room temperature. Now you've got tungsten metal with a lot of gasses dissolved into it and it is more brittle at room temperature than it would have been if it had never been heated in the first place.

I'm sure other metals act similarly but tungsten seems to be particularly bad after it has been heated (and cooled) in atmosphere.


I second this advice.

Here is an example I grabbed off of my web site. When working for the Physics & Astronomy Department of a university, I made these in a drinking glass filled w/argon to keep the glowing filament from becoming brittle as described.

http://i1096.photobucket.com/albums/g327/jhe-1973/Shop%20tricks/Tungstenfilament_zps07d48b0a.jpg (http://s1096.photobucket.com/user/jhe-1973/media/Shop%20tricks/Tungstenfilament_zps07d48b0a.jpg.html)

Alistair Hosie
12-22-2013, 03:03 PM
what Evan said is what I have been taught you are really attemting the impossible knurling cold tungsten can't be done I don't believe so anyway. Alistair ps happy ChristmaS

TGriffin
12-22-2013, 07:08 PM
Pure tungsten is sometimes used for ballast blocks on aircraft.
When I was working at a helicopter completion center we would occasionally have to install tungsten ballast blocks.
Usually the ballast would be secured using existing fastener locations, so we would mark the locations and send it over to the machine shop
to be drilled and reduced to the required weight. Never heard any complaints about it being difficult to machine.

I've actually done this. We needed a couple of counterweights for an airborne radar antenna and I use a couple of trapezoid shaped blocks that weighed about 60 pounds each. It machined like 304 stainless only softer and more gummy. HSS will cut it, but positive rake carbide is a better choice. I remember that if it was pushed too hard, the metal would just build up in front of the tool rather than form a chip.

Tom

Juergenwt
12-22-2013, 08:08 PM
We used this: http://www.ferro-titanit.com/en/home/

Ferro-Titanit® is the trademark used by Deutsche Edelstahlwerke
GmbH for machinable and hardenable alloys produced
by powder metallurgy techniques. Materials that have so far
been available for tools and wearing parts have included tool
steel and tungsten carbide alloys. Ferro-Titanit® material
combines the properties of steel and tungsten carbide alloys.
It is possible to machine this material by conventional methods in
the asdelivered condition. When hardened (up to 69 HRC), Ferro-Titanit® can
be used to economically solve many wear problems. The advantages of powder
metallurgy compared with usual melting methods - no fibering, no segregation,
homogeneous fine-grained carbide distribution, no impurities, etc. - allow Ferro-
Titanit® to be alloyed with one of the hardest carbides (titanium carbide) by as
much as 45% by vol. without losing the machinability