440C chisel edged knife bowed after heat treat

[harveyiceman]

Hello All, I am a newbie and have searched the interwebs for the answer to this question with vague results (sometimes it works sometimes not). I am an Ice Sculptor and as such use many cutting instruments to complete my work. Starting this year I have begun making and selling various rotary tool bits which led me to wanting to make an ice carving specific knife.

The knife I designed is made of 440C and is full tang with a 6" handle and a 6" chisel edged blade at about 20 degrees, the back is flat but hollowed slightly so as to afford easier sharpening. I drilled all of my pin holes and beveled the edge to about 1/32" before sending off to the heat treater.

When my steel returned from HT nothing seemed out the ordinary but upon closer inspection found that the entire knife bowed (concave on the backside) ever so slightly to one side (I have been told not to go back to that heat treater, but at the same time wonder if it is because of the chisel edge), almost unnoticeable. However, my perfectly flat scales do not fit so perfectly to the steels bowed condition.

My question now is "What did I do wrong, and how can I avoid this issue in the future?"

Thanks in advance for any wisdom you can shed on my plight. I am sure I missed a step or rushed the gun somewhere. The pic above is the condition they where in when I sent them of to HT.

[Ray Rogers]

Warping is caused by stresses in the steel, uneven grinds induce stress. There are other possibilities too, but in your case that seems the most likely culprit. The simple solution is to grind your blades post heat treat. I've always ground all my blades post HT, especially blades made from thin stock and rarely ever have any significant warpage. Grinding after HT also gives you the chance to grind out any slight warp that you might get from other causes.

If your heat treater offers cryo treatment you should have that done to your 440C blades. 440C responds very well to cryo and you'll get a tougher blade with better edge holding ...

[WBE]

I would find another heat treater.

[harveyiceman]

Thanks for the replies guys. While I was tapering the tangs flat I found that one of the knives had not warped, the one with the tag attached to it. How fine do finish the steel before HT? 220?

[ckluftinger]

I usually go to 120 before HT. After HT I do 120 again, then 220 and from there by hand to 1000 grit. As Ray said, it helps to do your grinding post HT. Takes a bit longer and uses more belts, but the heavier mass helps to prevent warping. Just have to be careful not to over heat the thin parts during grinding (edge and tip). Good luck!

[Fortes]

I'll be in new york in February. I would buy bars 440c stainless steel 1/8 thick with 2 and 4 inches wide. Can anyone tell me suppliers?

[Fortes]

Please send information to my email jmfadv@gmail.com

[Doug Lester]

Check with The New Jersey Steel Baron or Alpha Knife Supply.

Doug