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I coulda added on to the 4140 topic but would like to start my own here. There's two steels Grant turned me onto; 4140 as used in Off-center's swage dies (why doesn't someone ask what hardening method Kayne uses now?) and 8630. Similar to 4140, this stuff is supposed to be oil hardening. Similar to 4140, achieved hardness with oil quench leaves alot to be desired. Grant mentioned about water for thicker sections of 4140 and I would now concur. Unfortunately I never got to ask him about water quenching 8630. References list both methods and I'm wondering what you guys have used.

The dies I've made have differing sections of mass that I'm afraid may stress out. I water quenched a sliver of it and i would guess mid 50's Rockwell

I wound up going with what the references all say works very well for 8630: Case hardening with an oil quench. I'm guessing the business ends now are close to 60 rockwell and the core is still plenty soft.

We'll see how it holds up over the course of a few thousand rivets.

Why 8630? It's 2$ a lb at online metals~!

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I know there are lots of breaker bits made from 8630 and 8620...(Again Grants wisdom) They tend to be the 1" square ones used in Rivet Busters. When I heat treat those I do a "blacksmiths heat treat" in that I quench them in oil till I figure they are down to about 300 deg based on the oil smoke coming off and then let them air cool.. Pretty amazing toughness for such a basic HT operation. What size of material are you making the dies out of? I know its more money but I really like 4340 for high use dies and swages and I use it as forged. My ramp die I use for the bits is a un heat treated chunk of 4340 and I have done maybe 60 thousand bits on it only dressing it occasionally...

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Hey Larry,
Was wondering which of the bit styles were using it since most hex bits were always 1045 ish. I'd agree, the stuff seems tough as nails. Makes great tongs- springy as heck.

The dies I'm making have a head dia of 2 1/2" and a shaft of 1.5". Going to be a wait and see how well they hold up. Fortunately I made three die so they should buy me some time if there are failures.

Your buddy Jeff at Michigan Pneumatic says they make their rivet sets out of 4340.

The dies for your 3B are 4340M (cobalt mod) I got from Boeing Surplus for 25 cents a lb. 400 lb blocks for 100 bucks was too good to pass up. Although when Grant machined those he said they were xxxx hard; probably why they were at Boeing Surplus. Have you got a line on any of that material in rounds?

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