Telling the difference between C2 & C5 carbide?

If they have no markings, but each has a distinctive appearance, one thing you can do is take a cut on some cast iron, especially if the iron is slightly chilled. The C2 will handle it in stride, while the C5 will fall on its ass quite quickly. One you identify which color is what, you can sort the lot by that feature.

Harold

Tungsten carbide is bound with a cobalt binder; the binder is slightly magnetic, you might be able to tell C5 from C2 because the C2 has less binder (and is less magnetic).

That's an interesting idea.

I just tried it with some 322 inserts, one C2 and one C5, each new, still in the container. Both appear to have the same attraction to a magnet. I lowered the magnet directly over the inserts, sitting on wood. Each was lifted to the magnet at roughly 5/16" away. If there's a difference, it's not enough to be conclusive.

Harold