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air hammer die keys

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Made a new die key for the upper die in my air hammer. Used 4140. Use it annealed or temper it?

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Posted · Report post

You would have to harden it before you can temper it. I fit them hot and use them as forged.

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Posted · Report post

I agree with Peacock just remember they will loosen at first when you use the hammer as the scale and rough forged surface changes. When you are making the keys hot they should be kept as cleaan of scale as you can while you are making them. The last set I made a few months ago were out of some pretty high carbon steel and I did no heat treating on them. They have been working very well.

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I machine my wedges out of 4140 using the same master taper gauge for all the wedges, and use it to set the taper on the sowblock dovetail pin as well. I heat to high red and let cool to normalize, a good practice after machining. Then heat to orange and oil quench. I temper them at 400 degrees F for a half hour. The ends do not mushroom, which is why the wedges are heat treated.

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Posted · Report post

Thank you for all of your comments and suggestions. This is very helpful.

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I have a set of wedges that John Larson made as described above and have a different set that are mild and not treated. I have to redress the mild ones frequently. They tend to get a bow in them and gall easier. The 4140 HT dies just work and I have not had to redress them at all the usage being the same.

I use an 8 pound brass sledge to set and remove them.

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.
This really depends on how big the key is. On my Bradley the keys are about 1.75 wide and 1" thick at the big end and 18" long so they are big enough in as-forged condition to handle the pounding they get. If I were doing some of the thin keys I've seen on small hammers I'd heat treat them. Patrick

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