Question about fixing a warp

D

Daniel Swanson

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Mar 13, 2018
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I made a long blade out of 3/16” 1084 from Aldo and developed a nasty warp along the entire blade during heat treat. I’ve been tempering the blade with it clamped to a piece of metal with a shim underneath the curve to try to get the warp out. It’s working, but I’ve had to repeat the process up and down the length of the blade, and now it’s in the oven for the 5th time, at 400 degrees. I’m confident that the warp will be resolved after this cycle. But, is tempering 5 cycles going to ruin the Heat treat?
 
It won’t ruin the heat treat but the hardness will be lower then where it would of settled after 2 temper cycles.
 
I always temper first time about 30 under my target temp when fixing warps for this reason
If I get warp fixed on first temper I do second on target temp or usually it takes a second fix or third fix so I leave the temp lower
I
 
Hey everyone. So I made 2 woodlore type knife blanks out of 1084. Both have a warp that’s right at the tip. They’re both heat treated and tempered. I finished the scandi grinds on the first one. It’s the sharpest knife I’ve ever seen, but the warp is enough to make my grinds slightly uneven. I tried to get the warp out of the second one with three bolts in my vise. It’s 1 1/4” or so from the tip. I’m bending the knife pretty extremely in the vise over a small length at the tip of the knife and it just springs right back to being warped. Is there anything that I can do?

I can’t really grind it flat without removing.15 or more from the thickness of the entire blank. Should I clamp it in angle iron with the bolts to bend the warp out and just do a third temper cycle? I don’t have a clue what a third cycle would do to the knife in general or if it would get the warp out. I don’t really want to redo the heat treat if there’s another way. I’d truly appreciate any advice. Thanks!
 
Is clamp it to the angle iron and temper again. Same temp. Just make sure you counter bend the warp out with some shims... I used a stack of dimes last time I did it.
 
I have had success with additional temper cycles on carbon steel (80CRV2) to remove warps. You may have to over bend it a little bit. I don't think additional temper cycles can hurt much other than you might lose a little bit of hardness.
 
We surface peen our blades to straighten them. Using a carbide faced hammer you gently peen the inside curve of the bow and it will straighten right out. Then a light touch on the grinder to clean it up and bam done.
 
Temper straightening is a good method. There are several things that help.

1) Temperature. I read where people are doing the temper at 350 to 400 and can't get the warp out. Raising the temperature 25 to 50F degrees will help with a stubborn warp. Despite what you read, this does not greatly lower the hardness. Raising the temperature from 400 to 425F degrees should only drop the hardness about 1 Rc point. raising from 400 to 450F will drop 1095 from Rc 63-64 to Rc 62-61.

2) Bend ratio. Over bend the warp by twice the amount needed. If you just clamp or bend it straight it will not remove the bend. In some cases you may have to bend it more than 2X. It is best to do any more than a 2X bend after the blade has warmed above 300F for 15 minutes.

3) Time. Putting a clamped blade in the oven at 300F for 30 minutes won't do much or anything. Putting it in a 425-450F oven for 1 or 2 hours will. The total time for repeated tempering is really insignificant. Even if you accumulated 10 hours of tempering time working out a warp it wouldn't significantly affect the hardness.
 
I appreciate all the info. I’m glad to have run into such a knowledgeable and helpful group of folks.

I overbent the blade and retempered at the same temp which ended up around 405 degrees. (Sketchy home oven). It got almost all of the warp out.

This will be my sixth knife and probably the nicest one yet if I don’t botch anything attaching and shaping the scales. That’s progress; right? I can’t figure out how to post photos on here or Id show you all what I’ve accomplished so far.

I’m gonna need to learn how to make a sheath at some point.
 
Sam Brothers said:
I appreciate all the info. I’m glad to have run into such a knowledgeable and helpful group of folks.

I overbent the blade and retempered at the same temp which ended up around 405 degrees. (Sketchy home oven). It got almost all of the warp out.

This will be my sixth knife and probably the nicest one yet if I don’t botch anything attaching and shaping the scales. That’s progress; right? I can’t figure out how to post photos on here or Id show you all what I’ve accomplished so far.

I’m gonna need to learn how to make a sheath at some point.
Click to expand...

Easiest way of posting pics is using a third host (like imgur) and copying/pasting the link here using the image command (small image button above of where you write your reply).

There are great videos on sheath making on YouTube, Chartermade and Kyle Royer are the ones that helped me the most with tons of practical tips.
 
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