Are Set Screws hardened

Answer 1

They are always hardened as a general rule. This prevents deformation of the screws under stresses. They also usually have a black oxide treatment to prevent rusting. The fact that set screws are hard often has a side effect that causes them to "dig in" to contacting softer materials. This could be a good or bad thing. I am not sure exactly how hard they are, but they are very hard... as hard as a most drill bits (which is very hard), and they rupture under very high stress or shock with little elasticity.