Straightening O-1 blades after heat treat...

R.Markus

R.Markus

Joined
Sep 17, 2000
Messages
279
I searched around and found some good advice, but none of it was specifically for O-1. So here is my question:

I sent out seven blades for heat treat (a buddy of mine owns a big machine shop and the knives went out with a bunch of tooling he had heat treated, so it saved me money...although I was a bit worried that it wasn't a knife specific place). They all came back a little warped. Four of them I can live with and with couple passes on the grinder before I get back to working on the bevels they'll be fine. The other three are a bit longer (around seven inches or so of 5/32 O-1) and are warped enough that I'll have to try to straighten them to make them usable.

I've read clamping them so they are bent slightly opposite the warp (by using a shim at the blade tip or something similar) and putting them through a tempering cycle is the/a way to do this. Google searches have the tempering cycle between 350-400 degrees for two hours. I mainly want to make sure I do this right before I do it.

Here are the knives I got back. The three in question are the longer slender identical ones...

octknivespostHT-M.jpg
 
Ask your friend what temperature he used to temper them. 400F is a bit chilly for O1 unless you're looking for very high hardness, IMO.

You can bend them back with a simple softer-than-steel jig at tempering temperature - you have to bend PAST your target, of course. But I've only watched this done, not performed it successfully myself - I'm a bit timid about hauling off on 'em turns out. I imagine some of the real experts have more appropriate advice, but that's my limited experience.
Oh, and holding 450F blades is exciting.
 
Thanks for the info. The 350 and 375 figures I saw last night seemed to low to me. I saw on Alro Steel website a temperature range fromb350-500 depending on wanted hardness (it listed a range of 57-62).
 
Awesome. Thank you. That is what I was looking for. I don't know how I missed that last night with all my searching. I was also out in the garage looking for a suitable piece of metal to clamp to. I hadn't though about using an old file.

Now I just need to find the right temperature...I might be overthinking this too much. I did months of reading and research before I even bought any equipment or started making knives it's kind of funny I've read all this stuff before, but can't remember where to find it all again. :rolleyes:
 
400* Brother. Don't try to straighten it any less then that. :)
 
Thanks again. :thumbup:

There is a chart about 3/4 of the way down this page (the entire read is pretty good) that has temp vs. approximate hardness (if the the chart is accurate). According to it, maybe I should be closer to 500 degrees. I know I wouldn't do it any less than 400.

http://threeplanes.net/toolsteel.html
 
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