Tempering question

B

Blackdirt cowboy

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Oct 29, 2015
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I’ve got some 1084 blades I’m working on. They will be hollow ground with a very fine edge. I quenched them, then tempered them at 400° for two, one hour cycles. I don’t have a way to test hardness, but according to all the data I’ve seen, this should give me 60-61 Rockwell.

I’m concerned that it may have left the blades too brittle, for as fine as the edge is. Can I just pop them in the oven and retemper them at 450° To drop the hardness to the 57-58 range?
 
I would think so, but lest I am sticking my foot in my mouth because of something I don’t understand, I will watch for others (more experienced) answers..
 
It is best to test the edge at the current hardness. If they perform OK, then all is good. If they seem chippy in testing, retemper ar 425, and if still chipy, again at 450. The brass rod test is the simplest method of making the test.
 
Stacey, maybe explain the brass rod test for him in case he or someone else is unfamiliar with it.
 
The brass rod test shows the blade's hardness vs toughness qualities. It will show a proper HT and tempering.

Take a piece of 1/4" round brass rod and set it on a firm surface. It is simplest to just epoxy it on a board.

Sharpen the blade before final finishing the bevels or adding the handle. You want an edge that is a bit thinner that the final edge you will apply for use, so it can flex a little for the test.

Place the knife straight down on the brass rod and apply some firm side pressure to the edge. You don't want to push down hard, just enough to hold it against the rod.
Observe when the edge defects a bit. You don't need to bend it much, just enough to be visible.
Release the side pressure and observe if the deflection returns to center. Flex the other way. Don't do any one spot more that one flex both ways. Move to a new spot for additional tests.
Try it again with firmer sideways pressure.
If the edge returns to center and does not chip, the temper is perfect.
If the edge chips easily, the temper is too low. Retemper at 25 degree increments until it is right.
If the edge stays defected and does not return much at all, the blade is insufficiently hardened. Redo the HT. Dull edge back to prevent waffle edge.

In some cases of a seemingly chippy edge, merely increasing the edge angle a bit will make the blade pass the test.

When all is well, dull back the sharp edge and finish the knife.
 
Thanks, guys. I know they’re too hard as I’ve chipped the edge out of one just simply dropping it. I think I’ll retemper and then do the brass rod test.
 
Blackdirt cowboy said:
Thanks, guys. I know they’re too hard as I’ve chipped the edge out of one just simply dropping it. I think I’ll retemper and then do the brass rod test.
Click to expand...
I knife that passes the brass rod test can chip when dropped. Knives don’t Luke yo be dropped just to let you know lol
 
Thanks JT. That makes perfect sense too. I’ve got a blade that I ground to thin and got bacon edge when I quenched I’m going to use it to play with the temper levels and see what happens.
 
Blackdirt cowboy said:
I’ve got some 1084 blades I’m working on. They will be hollow ground with a very fine edge. I quenched them, then tempered them at 400° for two, one hour cycles. I don’t have a way to test hardness, but according to all the data I’ve seen, this should give me 60-61 Rockwell.

I’m concerned that it may have left the blades too brittle, for as fine as the edge is. Can I just pop them in the oven and retemper them at 450° To drop the hardness to the 57-58 range?
Click to expand...
Did you heat treat using a forge or a furnace?

Hoss
 
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