How far to take 440C prior to heat treating?

Bob Ohlemann

Bob Ohlemann

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Dec 5, 2013
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Finally getting started on some blades. The first few will be made from 3/16" 440C. I will have them heat treated by Texas Knifemakers Supply. They will cryo them as well. How close to complete should I take these blades before sending them to HT? Any advise on ideal edge thickness pre-HT for hollow grinds?

Bob
 
They do a really good job of keeping the blade clean, just light oxidation. I go to 400 and the final edge, typically 0.015. The blade is a light straw color when returned, I hit with 400 again and then do any additional sanding.
 
Yep Bob - just complete the blade other than sharpening. That's what I do for most any SS. I do my own HT, but I'm sure the commercial places will return the blades in as good condition as I can do.

Ken
 
Patrickknives said:
They do a really good job of keeping the blade clean, just light oxidation.
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That's good to hear. I've found the same to be true of blades coming back from Peters'.

RangerBobTX said:
So, I should basically complete the blades other than sharpening?
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Yes, you can even complete hand-sanding before HT. That will save a good deal of time. The oxide colors from tempering sand off easily. As long as your grinds are even and straight, and the edge isn't too thin (.015" is plenty thick enough) there's little risk of warpage problems.
 
Do I need to worry about stress cracks? Specifically, do I need to finish the area that will be hidden under the handle if I'm just going to be scuffing it up later for bonding the scales on? Right now that area has quite a few scratches from filing.

Bob
 
Just finish it as good as you would for the finished knife. Under the scales doesn't have to be perfect unless you have the drive to make it so, and it can have deeper scratches and such without much worry. So no, you don't have to hand finish it perfectly. I don't worry too much about stress fractures in 440 unless you have some big stress risers. Atmosphere or plate quenching as typically done by pro treaters isn't as stressful as oil quenching or something like brine quenching in fast steels.

--nathan
 
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