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How do I keep thin blades from warping during heat treating?

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22 June 2013, 07:55 AM
Josh Crain
How do I keep thin blades from warping during heat treating?
Hey, Folks! I got a question that, if I get an answer to it, will change my life for the better! Smiler I'm making a very thin bladed kitchen knife for a co-worker, and I've run into a problem: During the heat treating process, I heat the blade to a dull red heat, and then quench it in a five gallon bucket of oil. Even when I get an even heat, the blade will still warp, due to the fact that it's so thin. Any suggestions as to how I can prevent this? I'm getting pretty desperate here! Confused


"Return unto me, and I will return unto you," saith the Lord of hosts.
~Malachi 3:7b
22 June 2013, 12:27 PM
doublelong spring
Josh I am no knife maker and limited experience smithing.I am throwing this out in hopes someone else knows and since what you are doing isn't working. You are putting the work piece into a bucket type recepticle. No matter how fast you might be the blade is cooling at an uneven rate. Get a horizontal recepticle so you are more or less putting the whole piece into the liquid at once. I think I saw a sword maker on a tv show once also do this. Just throwing it out.


I never have been much for drinking the kool-aid.It's not in my nature.
23 June 2013, 06:05 AM
WBE
Josh, with very thin blades, you can expect some warp. Steel type and length of blade also come into the picture. With most steels, once your blade has cooled below 400°, you have a little time, which varies, to hand straighten wearing gloves. Once you feel rigidity in the blade, you must stop. Two ways to straighten afterwards. Do the tempers while warped, then clamp the blade to a thick piece of steel bar in such a manner as to be slightly over straightened by using a wedge if needed, then re-temper and quench in water. This may take a couple of trys. The other way is from Bill Moran, and is what I use. Do all the tempering you would normally do, then clamp the blade in the vise. It needs to be polished enough to see heat color. Determine the apex of the warp, and heat only the spine in that area with a propane torch to blue or gray, not allowing colors to get to the edge, over flex the blade a little past straight, and pour water on it. That will lock it in place. May take more than one try to get what you want. To minimize warp to start with, a point in quench, a stress relief heat below non-magnetic. 1250° for an hour if you have a HT oven. Good normalizing practices. Even grinds.
23 June 2013, 08:22 AM
Josh Crain
Thanks, Guys! And thanks to you, Wick. I'll definetly make sure to try those ideas out. I'll also look for some more on the sites mentioned. I'll let you know how it turns out!

~Josh


"Return unto me, and I will return unto you," saith the Lord of hosts.
~Malachi 3:7b
23 June 2013, 01:32 PM
doublelong spring
Josh it looks like you got some good advice. WBE the second way of straightening you gave is very similar to how we used to straighten I-beams back when I was welding.


I never have been much for drinking the kool-aid.It's not in my nature.
25 June 2013, 12:33 PM
GreyWolf
Josh along with Wick's advice try vertical quenching - a piece of 2-3" wide sewer pipe capped on one end works nicely as a quench tank (to heat the oil I just heat a 2" x 12" length of old iron wagon wheel and stick it in the oil without touching the plastic).
Hold by the tang and dunk with the blade held straight up and down - this is the way a lot of sword makers quench and it apparently aids in keeping long relatively thin blades straight...


aka Chuck Burrows
26 June 2013, 10:25 AM
doublelong spring
Well Josh let us know when you get a blade to work out.


I never have been much for drinking the kool-aid.It's not in my nature.