So much work, so much warp

[darlington.edgecraft]

This was my model “Candyman”. I spent all day grinding blades and tapering tangs just for it to turn into a banana in the kiln

 

[Stacy E. Apelt - Bladesmith]

If you think that is a banana, wait until you have a real warp.
Temper as normal twice and then put back for a third temper. Straighten while hot with thick gloves or Japanese Straightening Boards. If it cools and you have to do more straightening, put it back in the oven for about 10 minutes and straighten more. The extra tempering won't hurt anything. I like to do all straightening between 400°F and 425°F.

Everyone should make a set of Japanese straightening boards - post #12 and #15:

Thread 'Flattening Stock'

May 10, 2022

I have some 24" x 1.5" x 0.25" sticks of 5160 that came to me with a slight bow in them along their length. I cut a 9" section off for a full tang pattern, laid it out and roughed out the profile. The bow in the stock is still significant. What's the best/fastest/easiest way to eliminate this bow? I know I can grind it, pretty sure I can heat & bend it, but I'm kinda concerned about it showing back up as a warp after heat treat. Is one method better than the other? Is there a preferred "stress relief" temperature to shoot for if I heat it and clamp it? Thanks!

• Bühlmann
• Replies: 15
• Forum: Shop Talk - BladeSmith Questions and Answers

 

[Linus Knives]

A carbide tip straightening hammer will take that warp right out. After tempering of course.
Linus

 

[Fiddleback]

We use a carbide hammer. I believe she had hammered this one to death and still couldn't correct the warp...

 

[Deutron]

Hi,

I think there are several options to try :

a) Reheat the blade, normalize, straighten, then quench again
b) Straighten it via some sort of a jig before putting into a tempering, let heat to do the job
c) Temper, try to straighten while hot by bending
d) Temper, try flatten via a hammer while hot

c) can be risky due to breaking and d) can induce micro cracks if the steel is not soft enough

Regards