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08-24-2016, 11:53 AM
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Guru
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Join Date: Aug 2015
Location: ny
Posts: 1,438
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need to reharden knives
ok so ya know I was saying my blade was softer than I thought it should be and I thought it could be from trying to keep the tang soft that is not the reason as I said I HTed 12 blades 3 in the oven at a time I only tried to keep the tang soft on 2 of them and they were not in the same group of 3. when I grinded the other one it was hard as expected so I went back and check the other 2 that was in the batch of that soft one they were soft as well I don't know why I must have made a mistake somewhere with out realizing it. so now I have 3 blades that are soft still so I will have to go back and re harden it...looking at the 440c spec sheet there are instructions for annealing but I don't see anything for normalizing does that mean that normalizing is not required? so I just need to anneal and then start over a re harden??
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08-24-2016, 12:13 PM
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Skilled
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Join Date: Jul 2013
Location: NE Tennessee
Posts: 409
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if its already too soft I don't see why youd need to soften it before trying to harden it.
just run them back through H&T cycles.
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08-24-2016, 12:59 PM
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Guru
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Join Date: Aug 2015
Location: ny
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good point I have never had to do this before and I just remember people saying depending on the type of steel it would need either normalizing or anneal or both
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08-24-2016, 02:49 PM
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Founding Member / Moderator
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Join Date: Jun 2002
Location: Wauconda, WA
Posts: 9,840
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I guess you could try it again as they are but my first instinct would be to anneal them. I don't think you can't normalize an air hardening stainless....
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08-24-2016, 05:04 PM
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Guru
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Join Date: Aug 2015
Location: ny
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yeh I was kind thinking just anneal them even if its not needed I don't think it will hurt so probilly better to just play it safe and do it. the only down side is I am going to have to start early cause doiling the way the spec sheet says to heat to 1550-1650 at a rate not exceeding 400 degrees a hour so that will take 4 hours then cool to 1000 deg at a rate of 50 deg/hour that's 12 hours so 16 hours now I know I am not doing anything just waiting on the oven but I still got to be around for that time as I knw the oven is real safe and does everything on its own but I still don't like to have it going when I am not around I am going to have to wait a couple days I don't have the time to sit at home all day for a few days
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08-24-2016, 07:26 PM
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Hall of Famer
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Join Date: Sep 2006
Location: Decatur, IL
Posts: 2,612
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Ray's right, you can't normalize air quenching steel. A critical anneal, austenizing the steel and then allowing it to cool slowly, can run into problems with carbide clumping which could cause problems with drilling and getting a fine edge. You might try a sub-critical anneal where you heat the steel up to about 1300? and then letting it slowly cool. If you're not worried about grain growth you could just repeat the hardening process.
Doug
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08-24-2016, 11:50 PM
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Skilled
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Join Date: Jul 2013
Location: NE Tennessee
Posts: 409
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then don't just SIT.... work on something else.....
or watch movies and relax... checking oven between movies as necessary.
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08-25-2016, 12:30 PM
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Skilled
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Join Date: Dec 2015
Location: NC Mountains
Posts: 470
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You know, I am very impressed with your desire to work with stainless and learn the rather complicated process. Kind of toyed with the idea myself but decided for now, carbon and 0-1 are my preference. But you do know that there are services out there that will HT stainless and cryo treat for $10-$14 per blade right? May be something you want to consider at this start-up time to get some product finished, some knives to customers, and allow you to tinker with the HT. Seems "tinkering" around is best done with individual test blades as opposed to "batches".
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440c, 550, art, at home, back, blade, blades, carbon, degrees, edge, harden, heat, home, knife, knives, made, play, stainless, steel, tang |
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