Thread: How thin does a diamond needle have to be to be able to snap it?

I was playing with a mechanical pencil by pushing the lead out about an inch then pushing it back in like a vaccine shot. Then I realized I was doing it on my finger (not on a vain). I was wondering if you could stab a needle through your bone, I figured it was a no. But then I wondered if it was possible to do with a diamond needle that was really sharp. But I know the sharper it is means the thinner it is at the tip, so would a diamond needle stab through your bone or just snap?

diamond is very hard, but also very brittle. The needle would encounter some side forces, and it would shatter. A needle of hardened steel would be almost as hard, and less brittle, and would probably go through a bone.

There is no doubt that a sharp steel needle (like a sewing needle) will easily go through a finger bone. I have done it as a kid, hanging around a sewing machine and being too smart for my own good.

You could try it with a small hammer and a meat bone, using protective eye-ware and something to hold the needle square to the bone. It is possible the needle will break too. It all depends on alignment and direction of the force. A knife can cut bone too, especially a big one (think sharp machete or chef's knife). Note that bones get harder as they dry out.

The most outstanding physical properties of diamond are hardness and high thermal conductivity. The hardness helps it cut or abrade anything less hard. Steel is much harder than bone, so all that is needed. It is very unlikely you could obtain a needle shaped piece of diamond. Diamond particles are sometimes embedded in a steel (knife sharpener). Diamond toughness (resisting fracture due to impact) is 7.5?10 MPa??m. Glass is 0.7MPa??m, steel up to 50MPa??m. Diamond may have flaws too.