My first batch of knives came back from heat treating sporting low RC numbers

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Bob Ohlemann

Bob Ohlemann

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I got my first batch of knives back from Texas Knifemakers Supply this week. I had all eleven 440C blades heat treated and cryo'ed. They are all testing 52 to 53 on my Ames tester. My standard is testing exactly as marked (64Rc). So, is this too low for a useable knife? Will the cryo make them any tougher at these low numbers than a non cryo blade? I surmise that they will be easy to sharpen but edge retention will not be very good. How bad will they be? Should I finish the knives out and give them away to friends and family or, should I just scrap them? FWIW, not one of the blades had a dimple in it from testing by TKMS.

Bob
 
Bob, next time send to Peter's HT. :D

If they are infact 52-53, that's pretty damn low, personally I wouldn't finish them out, just my .02.
 
carbonsteel928 said:
Bob, next time send to Peter's HT. :D

If they are infact 52-53, that's pretty damn low, personally I wouldn't finish them out, just my .02.
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Mike, there won't be a next time. I have a brand new Evenheat KO-18 sitting in the shop ready to go to work. I feel pretty confident I can do better than this.

Bob
 
Bob, even by accident I've gotten high 50s lol. I'm sure you'll be able to hit your numbers without much issue. Hopefully they do the right thing and refund you your money; there is no excuse for this crap.
 
How do the blades look? Any chance they have excess decarb? More common with carbon steels but..... Try grinding into a tang a bit and re-test? Otherwise, if send em all back for another heat treat.
 
Brian Ayres said:
How do the blades look? Any chance they have excess decarb? More common with carbon steels but..... Try grinding into a tang a bit and re-test? Otherwise, if send em all back for another heat treat.
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The blades look really good; dark gray color, no decarb and nice and straight. One of the blades I tested after finish sanding to 400 grit so it was very clean. I have been doing some research and I can't even see how they ended up with numbers this low. Can I just redo them in my oven? I would definitely just try one at a time since I'm new to this.

Bob
 
If they austentized too hot, either from ignorance or poor temp control, you could have a lot of retained austentite, in which case cryo might get you another point or two. 53 is too soft. I wouldn't even finish them out, personally. If I could get it to 56, that would be enough to finish them for friends/family, for me.
 
Bob, Have you called Texas Knife Supply? They heat treat a lot of blades. They couldn't get away with these kinds of numbers for very long I would think. They have an expensive custom built heat treating setup for stainless steels. I am wondering what could have happened. Please let us know what they say. You deserve both an explanation and a refund in my opinion. Larry
 
Is your hardness tester giving you the proper readings ? Do you have a test block to verify it ?
 
I have not had a chance to talk to Texas Knifemakers Supply yet. I wanted to know where I'm at with all this before I give them a call. Sounds like the blades are un-useable as is so now I need to decide how I want to proceed. I have a lot of time in these blades so, I really don't want to scrap them. I didn't expect the Evenheat to arrive for another month which is why I sent these out. If they can be re-treated, I'd rather do it myself.

Mark, I can not say with 100% certainty that there is not an issue with my tester but, it reads accurately on both a 43Hrc and a 64Hrc test block. I checked it several times while I was testing these blades.

Bob
 
Call TKMS. You shouldn't have any issues with them from a new HT. Let us know what you find out.
 
Call Brad at Peters Heat Treating and ask him if these can be re-heat treated. I would think they can.

Tim
 
There are about half a dozen reasons you could be getting low numbers and only one of them involves TKMS botching the heat treatment.

What is the model and number of your tester? Did you follow the instructions carefully? What size are your test blocks? Did you test all your blades? How do you know there is no decarb? Do you have any other stainless around you could have mixed up? What is your hardness testing procedure? Did TKMS know your desired hardness, or do they have a standard procedure they followed? Did they know the alloy you were sending? I know thats a lot of questions, but ya gotta start somewhere.
 
Whatta revoltin' development...................

Hopefully these can be redone and salvaged.

I was sad to read this after seeing the dandy blanks you'd ground out.

C
 
So we're past the part of "Am I doing something wrong". I'm not. I know how to test the hardness, my tester is accurate, the blades are clean, and I am very confident that the steel is 440C. TKMS knew what the steel was as it was clearly marked on the order and written again in the special instructions. I did not specify the hardness I wanted as they specify that they will harden to 58-59 unless otherwise requested. I am not trying to bash TKMS, mistakes happen; I will get this sorted out with them. My question is, what can I do about it now. Can the blades be re-treated or are they now junk?

Bob
 
It is your stuff, so it is ultimately your call, but I wouldn't retreat them yourself. Allow TKMS the opportunity to make it right.

Chris
 
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