[MikeK]

Originally Posted by d.j. moordigian

Mike,

Can you tell me the difference of the rivets, before and after annealing, on the
Rockwell?

d.j., I auctioned off my big Rockwell and Brinell floor model hardness tester when I closed up shop 12 years ago. (got $35!! ) If you want to play around and get a feel for the difference, take two grade 2 cold headed 1/4-20 bolts. Heat one bright red, let it cool slowly. Take both to the anvil, hold them sideways (pliers/tongs, not with fingers!) and whack the heads with a hand sledge. You'll see.

It's actually a bit more complicated than just starting hardness. Malleability decreases in a non-linear relation to apparent hardness in metals/alloys that work harden as hammering (cold forging) progresses.