flame straightening

S

SHOKR

Joined
Feb 13, 2013
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hey guys

i send my work to a HTer who can do a not-so-good job from time to time
in the past period i got back from him seriously warped blades in Sverker21 (d2) and 55Cr3(5155) so far these range from 8-20" OAL

i was going to go for the heat in oven with clamps and shims but someone suggested flame straightening method, anybody tried that before? any info or tips?
i checked online but didnt find a good source of info, specially since all the sources i found were speaking about non tempered steels

thanks
 
There are a few posts on straightening for minor warping. I believe nick wheeler has a step by step sequence that should sort you out. You might to find another heat greater or get your own heat treat oven. Or maybe ask to have certain procedure followed to minimize then chances.
 
Alo,
"Flame" straightening is an older technique where you spot heat a section of spine on one side only and dump water on it. The hope is to get it to reverse-warp. It works so-so at best, and can ruin the HT if not done carefully. I think part of what made it popular was Bill Moran (famous USA knifemaker) did it. Bill was a great guy, but was an old school blacksmith type knifemaker. I don't know that he ever understood metallurgy to the degree most newbies get exposed to it today.

A far better method is to heat the blade to 400F and straighten while hot. Repeat the heat and bend as needed to get it straight. A couple pieces of 2X4 boards with slots cut in them is a great tool to bend and twist a hot blade with. For minor warps, the clamp and heat will work, too.
A search for "Straightening warped blade" should get tons of reading material. Here is the Bladeforums search engine - https://www.google.com/cse/home?cx=011197018607028182644:qfobr3dlcra


تكون آمنة
 
PT Doc, thanks
i was just checking a piece of info when others suggested that technique and it seemed very interesting. as for my heat treating oven, just bit more money and i may be able to do my own smaller/medium blades :) and i did ask for certain procedures, he is what we call 'knows by heart but does not understand' :/


Stacy, thanks a lot
wouldnt 400F ruin temper? (i dont know the temper heat the guy used, but he brings out 60+ HRC for D2 and i dont know the other HRC for 5155)
and i guess heat with clamps can work, i mean all i really need to do it now is oven thermometer
will check out the search engine too

thanks for taking the time and translating too :)
 
400°F won't affect the temper. D2 is tempered at 400-500F for the lower tempering range ( best for knives) or 950-1000F for the upper range ( best for tooling and dies).
Most all knife steel is tempered in the 375-450F range.
 
Actually Bill knew an awful lot about metallurgy. Flame straightening can work, but there are much better methods. Such as Nick's tutorial, and straightening at 400 out of the tempering oven. Just need to go slow and not overdo it.
Good luck Ahmad.
 
Brion, thanks and nice to see you here :)

flame straightening did seem more interesting and that was an instant hook for me
i dont have HT oven, will try with regular kitchen oven the straightening method on a small blade and see :)

and wow, looks like you have Phd in knife making!

edit: how do i know if i was successful or not, or to rephrase, how do i know if i ruined the temper or not?
 
can someone please link me to Wheelers straightening thread, cant seem to find it and ive been searching for more than half an hour
 
NEVER try to straighten a warped hardened part at less than 400F !!
Flame straightening of anything but low carbon construction type steel should not be attempted !
Heat to at least 400 F but don't exceed the original tempering temp and straighten with clamps.

I remember working on a job where a flat piece was split like a opening book in an attempt !
 
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