straightening blades after ht

wnease

wnease

Joined
Apr 22, 2004
Messages
878
This comes up from time to time but there are a host of different solutions. I've been told to straighten cold in a 3-point set up, also to straighten warm, also to straighten cold and then warm with a torch and cool in the 3-point, also to pound the high side with a hammer using a soft anvil, also to touch high spots with a torch...

I'm talking about through-hardened blades of course. I've had the best success with straightening cold (banite blades tho), and today had some luck with straightening O-1 at 400 F, but just snapped the tang on an S30V blade at 400F (beautiful grain structure btw... always happy with my heat treater except for the occasional warp).

If you have experience please advise... even better would be an explanation of why some methods work and others don't.

Thanks!
 
I've had my best luck with a 3 point setup, with the blade as hot as the temper was.
Haven't snapped one since.
 
On ss blades I put them on a magnetic chuck right out of the quench. This eliminates most of the warpage. Some guys use big aluminum quench plates in a wood workers vise. I'd ask you heat treater his techniques and ask why the blades are coming back warped.
 
I often have no flat spots on my blades so a plate quench will not have enough surface contact for conduction. My heat treater uses a controlled atmosphere quench and the blades are hung on hooks.
 
I use some 6061 Aluminum jaws I made to replace the jaws that my 6" vise came with. I also rounded one side of the jaws and use the vise slightly opened to put light pressure to straighten blades (A2 steel though) and have never actually snapped a blade even after it dropped below 300 degrees or less ! There is actually a hell of a lot of time to straighten after cutting open the SS foil. I do not plate quench any longer as I find they come out warped when thin anyways !
 
Thanks for the thread, I like to just break-um:eek::D. I will try the heat and three point thing. Again, thanks
 
One of the things I forgot to mention is I do not grind in the bevels pre heat treat. I only profile and drill.
 
Having to straighten blades can always be anoying but here is a great way that Bob Egnath used to teach. Use the three poins but use concentrated high heat at the offset and only on the spine.You will need to go to red. You may actualy hear the blade "tic" as it kicks straight. Leave it to cool. It will not affect the blade edge heat treat. Frank
 
Wade Jones said:
Anyone got a picture of their 3 point setup?
Looking for some ideas to build my own.
Click to expand...

Wade... this is what I use. It's just three segments of aluminum rod that I bent to sit over the jaws of my vise. Easy to remove when not in use.
4340433681_cdbc5e0673_o.jpg


Concerning warpage during HT...

I am a newer knifemaker, and I currently only have experience heat treating 1080 and 1095 (none of those fancy steels y'all are using), but...
I almost never have warpage from the quench these days. I used to occasionally have the problem, but recently I started doing multiple stress-relief cycles (for these steels, soak at 1200F and cool to ambient) prior to my final quench cycle. Any warpages that are going to occur show up early in these stress-relief cycles and are easily fixed before the blade is quenched/hardened. I usually run three stress-relief cycles - not because three is a magic number but because, in most cases all warpage problems have disappeared after the third cycle.

Does anyone else run similar cycles prior to hardening?

Erin
 
For S30V? That's going to be a pain. You can hold it at 1250F for 2 hours to speroidize, then gently hammer it flat, and back in the oven for stress relief. Heat treat again until you get it right. I've broken a few blades and the grain size actually gets finer the 2nd time you heat treat it.
 
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