warping

Hi. I was posting on Eds forum but thought other newbies (like me) would appreciate it over here.

I am using 1084 steel and stock removal. I heat treated my blade yesterday.
I suspended it on a wire through the tang and heated it with two oxy acet torches thinking I would get an even heating on both sides to prevent warping. I heated it to critical temperature (lost magnetism) but saw that it had warped. I went ahead and quenched it in peanut oil thinking I may be able to bend the warp out later. I then tempered it in the oven at 420 F for 2 hrs (using a thermometer in the oven to double check the temp). I kept an eye on the colour whilst tempering and it was a yellow straw color and the oven temp was a constant 420 F. After cooling I saw that the color was blue!!!!!

Three questions:
1. Can I fix the warping and how (its shaped like a bananna)?
2. Given the colour of the blade after tempering, was 420F too hot? I read somewhere that 450 F was recommended so 420 I thought was on the low side.
3. Why did it warp?The profile was pretty much even....could the heating have been too aggressive?
Should I scrap it and start all over again........
this is my 5th attempt at making a blade, (for various reasons I binned the others including one other that warped then snaped when I tried to straighten it).....

Any knife makers in mid Florida (an hour north of Orlando)that I could visit, watch and learn?

When I heat treat I use only one propane burner and a pile of fire bricks I stack together for a small forge. I stick my blade in and heat from the back of the blade to the edge holding it parallel to the flame and heating slowly. I also normalize a few times in case there is any stress from the heat of grinding or uneven grinds. Normalizing has helped my warpage problem drasticaly.

When I use 1095 I temper at 400 deg.. After a few test blades this seemed to work the best for me, and I still check every blade with the brass rod test. If your heat up and quench isn't done properly it will have a direct effect on your tempering outcome. I found when I started out and heat treated my first few blades I was over heating before the quench. This was causing the blade to not cool fast enough and not harden completly. After a temper at temperatures recomended for the steel I was using, it came out soft and usualy a dark staw or brown color. I now watch close for color changes when heating and check with a magnet often. When it becomes non magnetic I make sure the entire blade is even in color and quench.

I'm only a rockie and have only made a hand full of knives, but maybe hearing some of the problems I've run into will help out. I'm sure one of the pro's will step in and give you some real advice.

Rick

Any asymmetry in the grind, or uneven heating, can be the cause of warpage.

If you have a machinist's vise near where you are heat treating, leave the jaws 1/4" apart. If a blade is obviously warped, while it is still VERY HOT, put the blade in the gap in the vise, and using your tongs, pull it in the direction it needs to go to straighten out. Then heat it back up to critical before quenching, unless it is an air quenching steel, in which case you can just let it continue to cool down.

Thanks for the replies.

Rick....I think maybe I am heating the metal before quenching a bit too fast. I have been suspending it with wire whilst heating then lifting it by the wire to quench (I havent any tongs yet). I like your idea with the fire bricks...I think I will experiment with that method and invest in some tongs.

John......I will try heating and bending in a vise but it is bent like a bananna...it needs some major work to straighten it!

Out of interest, I hear "edge quench" being mentioned. Would I be right in saying that I heat it as if I was going to do a full quench, but quench the edge instead?.......Do you let the back cool down in air (1084/1095 stock removal) or do you slowly immerse the whole blade?

Thanks.
Kevin.

Trail angel,good to see another maker from Florida..Try the FKA site for makers in your immeadiate area.And you can contact me and I will try to help you the best I can.Dave

www.floridaknifemakers.org/

If your over grinding your blades before heat treating that could also give you more chances warping. You can leave them a little heavy and grind after HT just don't let the blade get to hot. Ray