Heat treat thickness

S

smorgan345

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Mar 8, 2007
Messages
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I got a little crazy on my filing, I think I may have thinned my edge out too much for heat treat! How thin is still acceptable? what happens if you heat treat with too thin of an edge? It's 3/32" thick 440c bar stock but I've filed the edge down to less than the thickness of a dime which is what I read you should try and maintain. it's probably about 1/2 the thickness of a dime, maybe a little less in some places. I did 3 of 5 blades like this, please tell me I'm not screwed. Thanks for any input.
s
 
I've successfully had them down thinner than that for ht, 440c, commercial ht with inert gas for the quench. I am careful to sand them to 220 grit or better, lengthwise, to reduce stress risers at the edge going into the quench.
 
With 440-c you should be fine,I usually take mine down to .020-.025 before H/T.That's about half the thickness of a dime. The dime thickness rule is mostly for carbon steels to allow for decarb.
You cand also do a lot of your hand sanding before H/T also,I usually take mine to 400 grit.
Stan
 
thanks guys, I'll let know how it goes. Just to know, what's an inert gas quench? I'm heat treating with a kiln but was just going to plate quench? thanks for all the info.
Scott
 
smorgan345 said:
what's an inert gas quench? I'm heat treating with a kiln but was just going to plate quench? thanks for all the info.
Scott
Click to expand...

Cold inert gas is blasted into the chamber containing the austenitized blades to quench them, I suspect that the actual temperature change rate may be slower with the gas than with the plates (plates suck heat out really fast where they touch the blade) except at the edge of the blade, where the plates don't contact, your blades should be fine (unless they are chisel ground)

Don't worry too much, what's the worst that could happen?
 
Your blades will be fine. A well wrapped and plate quenched blade can go into heat treat almost at finished dimesions and finish. Coming out, it will need little more than a buffer to finish it up. Check with your heat treater to see what their preference is.

Rob!
 
I recommend grinding your blades hard. No reason to grind your blades two times and if your blade is less than 10 inches in length and less than 1/4 inch thick, Grind it hard .You won't have nearly as much trouble with warpage or inconsistent H/T. It is much easier to clean up your blade flats and I feel it is easier to grind the blade after H/T. Just take the necessary precautions to keep it cool while grinding.
There are a few exceptions when grinding hard is not recommended but that is not the norm. Give it a shot and see how you like it .
 
Hi. I have also filed my bevels too thin but I am using 01. Is this a problem for me? I am going for a professional HT.
 
A quick pass or two across the belt will thicken up your edge real quick, without removing so much metal you have to totally re-grind after HT. Use a fine grit so as not to put deep scratches in the very edge, which could contribute to warping or even cracking.

KnifeMaker.ca said:
Your blades will be fine. A well wrapped and plate quenched blade can go into heat treat almost at finished dimesions and finish. Coming out, it will need little more than a buffer to finish it up. Check with your heat treater to see what their preference is.

Rob!
Click to expand...

I agree. I grind my edges much thinner than a dime pre-HT and have had zero problems with warping. Check with your heat treater to see what their preference is.
 
wnease said:
Cold inert gas is blasted into the chamber containing the austenitized blades to quench them, I suspect that the actual temperature change rate may be slower with the gas than with the plates (plates suck heat out really fast where they touch the blade) except at the edge of the blade, where the plates don't contact, your blades should be fine (unless they are chisel ground)

Don't worry too much, what's the worst that could happen?
Click to expand...

would that be the same as just blowing them with compressed air or is it a specific type of gas? Someone mentioned hitting the blade with compressed air while it was being plate quenched. Do you think this would help with the edges?
 
thanks guys awesome info, I'm racing against the clock to get these done for Xmas presents. I'll post pics when complete, probably in the middle of the night xmas eve judging by the speed of my progress thus far. Lesson one in knife making for me, take however long you think something will take and double it. I just hope I don't blow it on the HT, I have no margin for error at this point.
 
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