W1 Lathe Chuck Keys - Heat Treat

Generally, steel does expand when hardened, that means tapped holes do shrink, for that reason, oversize taps are used in die work.
 
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Any suggestions for what Rockwell hardness I should aim for? A nice guy I know that has an oven is going to harden them. thanks. -John
 
Why are you making the key harder than the driver key sockets on the chuck? I'd rather see the key slowly wear out than the chuck, but that's me.

Without heat treating, W-1 is reasonably stainless.
 
I guess because I don't know any better. I know thats a bit of a lame statement but it's the truth. Plus, I just want them to last. There isn't s lot of play so I don't think they'll wear out the chuck. I could be mistaken.

It's a small chuck and I don't over wrench anything and still my last key (albeit, made from mild steel scraps) twisted and became trash fairly quickly. Could have been my fault as the square bit at the end was about 2 inches)

Thanks.
 
4140 HT at RC30 is perfect, not harder than a good chucks socket and will last forever. No heat treat necessary and still easy to machine. I made a few keys for my D1-3 and Cushman chucks out of mystery metal, probably 1018 or something. They didn’t last long. Square drives twisted. The 4140 ones look like new after 5 years

4140 ht and stress proof are my go to for stuff I don’t want to heat treat and 12L14 for detailed little bits, screws and such. High carbon steel has interesting use too, also turns nice. I pretty much reserve tool steels for stuff that I send for heat treat. It’s just so expensive.
 
I think next time, if I make any more, I'll go pick up a length of 4140. Sounds like the perfect material. This was a fun and first real machining project that I actually needed and I had some W1.
 
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