High density/mass material

[toolmaker35]

Hi guys. I've been working on a design for awhile now, and have most of the details down at this point, but am running into one problem. Part of this project uses 2 rectangular blocks of material about 4" x 2 1/2" x 1 1/4". I would like these to be wear resistant, needs to be machinable (conventional methods), and also need to be dense. A heavier weight to size is preferrable. I have looked at using tungsten carbide, but the blocks will need blind tapped holes and some contours which dictate EDM work (wire and sinker). I think this will blow my budget (I'm borderlined right now, on paper at least). I've also looked at tungsten steel (NoChat), but apparently it can only be had up to a hardness of 30 R/C. Is there a material which can be milled, has the mass of carbide and can be heat-treated to around 56-60 R/C? Or is this the dreaded "Unobtainium?" I've also thought about "slugging" blocks of D2 (or the like) with carbide round, but I think that would be a last ditch effort. Any ideas? Thanks in advance for any help.

[beanbag]

slug with lead instead?

[ikdor]

Make it hollow, fill with lead shot?
Or use depleted uranium, not sure how hard that is though.

Igor

[BobL]

Make it hollow, fill with lead shot?
Or use depleted uranium, not sure how hard that is though.

It's harder than RC30. I've cut 1/8" diam uranium wire with a workshop guillotine and it's almost as hard as spring steel.

Id go with lead slugs.

[Black_Moons]

Agreed, Weld yourself up a nice box, Melt lead into it, heat with a large torch to ensure all the lead inside melts into a huge mass and all the air gets out. Ensure the steel box has enough strength for whatever you wanna do, because the lead isent gonna do much besides keep it from collapsing in on itself.

[DATo]

Look into a material called nylatron (it is easy to find). I don't think it will have the density you want but as others have suggested you could probably add some weight to it one way or another if weight alone is the issue with regard to "density".

EDIT: Long ago I designed a cam whose wear surfaces (originally made of hardened tool steel) were made of nylatron inserts. The nylatron worked well in terms of economy and efficiency regarding repair; also, currently, in our shop, we have home made nylatron pads on the bottom of our cut off saw's portable stand which is used to support long bars and which is slid all over the place on a daily basis. The nylatron reduces surface friction on the tripod of legs to the point that you can slide it effortlessly from one place to another.

[Duffy]

Years ago, Atomic Energy of Canada used a form of sintered tungsten as high density radiation shielding. It was machined to form such things as Cobalt Therapy Unit focussing shutters. I was told that while hard, it machined like cast iron. They used it literally by the ton.
I have no idea where you would obtain it. This is NOT misnamed tungsten carbide. I have a piece which was used as a spacer block in a cobalt 60 shipping container. It is 1 3/8" diameter by the same height and weighs 550 grams.

[philbur]

Do you need the high density for increased load, increased inertia or reduced vibration, or some other reason? More information on the application might result in somebody spotting the none obvious solution.

Phil

[ammcoman2]

Bronze? Fairly dense.

There are some even more wear resistant than 660 - unfortunately they cost more!

Geoff

[toolmaker35]

Thanks so far, guys. I know that I'm being vague on the details of this, but it is a prototype & there is a niche market. The hardness of the parts is for wear resistance. These blocks will be a reference surface. They will have a pretty open tolerance (+/-.002" should be fine) on actual size, but they have to be matched within .0002" or less and stable once assembled. The added mass isn't critical, but it is desirable. Has anyone ever machined tungsten steel? From what I've read, it machines similar to tougher cast iron. I haven't priced it yet (big factor) or found out how stable it is (bigger factor), but for the prototype, it may work. Obviously, I still have some homework to do on this. Any more ideas, I'm all ears.

Edit: Wow, I type slow. Thanks for the replies, guys. The added mass would be to stabalize the part being referenced (odd geometry).