Blade Straightening

[bhartley]

I’m trying to finish my first proper knife, and I foolishly ground too much material away before hardening, now the blade is too thin and keeps warping when I quench it.

I am working with salvaged leaf spring steel which I am assuming to be 5160.

I am using new vegetable oil at 130F-160F for the quench. Quenching the whole blade seems to produce less warping than an edge quench.

I don’t think I will be able to quench the blade without it warping. How much will I be able to straighten the blade after tempering to 350F?

[Donnie]

Straightening after HT?.......Hope your luck is better than mine. I'm not saying it can't be done. It's just never worked for me.

[JPH]

Hello:

Where is it warped and what kind of warpage are you talking about..?

I straighten a lot of blades with not problem at all..All depends upon what type and direction of warpage you are talking about..

Any chances of a photo showing the area(s) involved??

JPH

[steve sells]

one trick when I screw up a blade (pun was intended) is straighten while its hot, IE an interrupted quench. You allow it to quench as normal BUT remove and straighten before it cools below 400 to 500F, then temper.

[Rich Hale]

That material may have some of the original spring shap0e left in it, if that is how it wants to bend when you quench it. Get it hot and straighten it, normalize two or three times and then try and harden it. Make real sure you push the blade into the oil straight and not move it side to side as it drops temp. After you harden it if there is a wee bit of bend you have a few seconds after you temper to take the bend out. Since you said it was thin already you best option may be to mark it tuition and hang it on the wall and start fresh.......

[bhartley]

I can't seem to take a picture that captures the warp. I went ahead and straightened it out with the hammer, and of course I got carried away and cracked the blade. I may be able to salvage it yet, but it isn't the knife I had in mind.

Anyway, I learned a lot and was able to get the next knife in the pipeline up the same level as the warped one in no time. I left it thick before the quench and the warp was very slight.