Re-Tempering O1

A

AndrewTheScot

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Jan 22, 2022
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Will I have any problems re-tempering a blade made from O1? It’s sitting at 61 Rockwell, but given the size of it (it’s a kukri), I feel that for as much impact that it will probably encounter, a 58 Rockwell would probably suit it better. I’m just curious to know how o1 behaves if you throw it back into the oven.

Thanks.
 
AndrewTheScot said:
Will I have any problems re-tempering a blade made from O1? It’s sitting at 61 Rockwell, but given the size of it (it’s a kukri), I feel that for as much impact that it will probably encounter, a 58 Rockwell would probably suit it better. I’m just curious to know how o1 behaves if you throw it back into the oven.

Thanks.
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It will continue to get softer with tempering temperatures.

Without hardness testing we can't quantify exactly how much but it will be softer.
 
DeadboxHero said:
It will continue to get softer with tempering temperatures.

Without hardness testing we can't quantify exactly how much but it will be softer.
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I’m not sure I understand your reply. Are you saying that putting it in at a higher temperature, say 425°-450°F, will in fact soften it to the desired hardness? Orrrr are you saying that any length of time spent at any desired tempering temperatures will continuously reduce hardness just because I’m reintroducing heat. My oven regulates heat pretty well so I can hold it pretty consistently at 425°-450°F, which according to the heat treat data, would put me around a 58 HRC. I wouldn’t be re-tempering using a forge or blowtorch if that was in question.
 
You won't have any problem re-tempering O1 at a higher temperature. If you wanted to start all over and re-quench, that would be difficult at best. The same holds true for most steels we make knives from.

61 isn't an unreasonable hardness for O1; 61/62 is what I usually shoot for. I've never broken an O1 blade - even edge chipping has been minimal. At 58Rc (assuming the rest of the heat treat went well), it will be insanely tough!

If it was my personal blade, I'd roll with it at 61 & see what kind of abuse it can take. There's so much more than hardness that goes into the overall usefulness of a blade.
 
Sam Dean said:
You won't have any problem re-tempering O1 at a higher temperature. If you wanted to start all over and re-quench, that would be difficult at best. The same holds true for most steels we make knives from.

61 isn't an unreasonable hardness for O1; 61/62 is what I usually shoot for. I've never broken an O1 blade - even edge chipping has been minimal. At 58Rc (assuming the rest of the heat treat went well), it will be insanely tough!

If it was my personal blade, I'd roll with it at 61 & see what kind of abuse it can take. There's so much more than hardness that goes into the overall usefulness of a blade.
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It was actually a batch of blades heat treated at peters heat treat. The small everyday carry blades I wasn’t worried about being 61-62 HRC. It was the swordlike kukri. I’m worried about it’s impact resistance when chopping. Thank you for the intel. I greatly appreciate it.
 
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