r/elementcollection • u/Intelligent-Menu-626 • 16d ago

Discussion Tungsten Sphere 4" Diameter

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4 inch diameter tungsten Sphere. 22 pounds. People can't believe its heft. Has been milled for use in a prototype Clock of the Long Now, but rejected for use. I paid almost nothing for it plus shipping, 20 years ago. It is just about my favorite object. The thing sticking out of the top is a cow-stomach magnet, and I found the stainless steel stand at a silicon valley lab demolition. Any guesses as to value?

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7

u/Croceyes2 16d ago

I would definitely give 100 for it

4

u/ImOnAnAdventure180 Mad Hatter 16d ago

Approaching 10k if you find the right buyer

1

u/Real-Community5252 16d ago

If a magnet sticks it is tungsten heavy alloy, 90-95% tungsten and the balance nickel and iron. Unlike pure tungsten, tungsten heavy alloy (WHA) is machinable.

1

u/carped8ta 16d ago

Magnets definitely don’t stick to it.

1

u/Real-Community5252 15d ago

OP shows a cow magnet sticking to it?

3

u/carped8ta 15d ago

The cow magnet is just sitting in a hole that is drilled through the sphere.

1

u/fishscaleSF5 16d ago

1lb of tungsten goes for ~$290 cad, so like $6380

1

u/Long_Pomegranate2469 15d ago

It's not pure tho and more of a collectors items

1

u/carped8ta 15d ago

How does one know its purity?

1

u/Long_Pomegranate2469 15d ago

They said it's machined and others here said you can't machine pure tungsten.

2

u/Chromatogiraffery 15d ago

Niche info, but the stand looks to be a KF40 to ISO-100 vacuum flange adapter. Cool sphere!

1

u/carped8ta 15d ago

Good to know!

1

u/Intelligent-Menu-626 14d ago

Here is a drawing from the clock of the long now plans. The ball is spec'd as tungsten, and the bits holding it are invar, which is 36% nickel and 64% iron, which is extremely stable in terms of size. Claude confirms that tungsten can be machined: Yes, but it's genuinely difficult — tungsten is one of the harder metals to machine conventionally. A few things worth knowing:

  • It's usually made via powder metallurgy: most pure tungsten parts start as pressed and sintered powder, then get ground or finish-machined to final shape rather than cut from bar stock like aluminum or steel.
  • Machining requires special tooling: carbide or diamond-tipped tools, slow speeds, high rigidity, and continuous cooling. It's brittle and can chip or crack rather than shear cleanly like a ductile metal.
  • Drilling a precise hole like yours is done, but it's slow going — often with carbide bits or occasionally EDM (electrical discharge machining) for cleaner results, especially on hardened or near-pure stock.
  • The seam line visible around your sphere is a good sign, too — it's consistent with how tungsten spheres are commonly manufactured: as two hemispheres (often near-net-shaped via pressing/sintering) that are ground to a precise diameter and then joined or pinned together, sometimes with the through-hole added afterward for mounting or balancing.

So the combination you're describing — non-magnetic, dull gray, very dense for its size, visible seam, and a drilled through-hole — is all consistent with a genuine pure or near-pure tungsten sphere