Knife bending question

Lerch

Lerch

Well-Known Member
I had my first knife bend a little bit in heat treat today, it is just the tip and just a little bit but enough to really bug me. I didnt notice it until i took the knife out of the foil wrapper and it was fully cooled. It is cpm154cm and i tempered it at 500deg so on after it took it out of the oven on the temper cycle i tried to bend it and i seemed to take most of the bend out of it. what is left i tried to take a picture of, here ya go

photo-8.jpg


are there any other tips on how to take that last little bit of bend out of the knife? i dont wanna apply too much pressure and break it off, but i also dont wanna grind the bend out as it would really change the look of the blade.

any ideas???? sorry the picture stinks, Iphone and im at work lol

thanks
steve
 
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There are others her that are more knowledgeable than myself but I will take a shot at this anyway. I am not familiar with the steel and its characteristics so it makes me hesitatant to suggest counter bending it at this stage of the game. But I would suggest this based on past experiences. Your best bet may be to anneal the steel and go through the quench and re heat treat the knife. Usually the heat treat process is not where you get the bend it is in the quench process. I am wondering if it was not already slightly bent and you may have not noticed it and the HT just made it stand out it even more.
I am sure that someone who is familiar with that steel will be able to give you suggestions! Maybe better than backing up and redoing!
 
This is a problem that frequently comes up. Because it didn't snap when you tried to counter bend it I would say the it's tempered well, though I don't have any heat treating info for the steel that you used. You could alway take it up to the tempering heat and try again until you're satified. You could make a straightening jib that will hold one metal rod at the apex of the bend with two other rods on the other side of the blade in a vice and slowly tighten it. However, that method can have the sweat beading on my forehead when I use it with carbon steels. I would get really nervous about it with stainless steel. The safest thing is to anneal the blade, you cannot normalize stainless steels, straighten the blade while hot, then reheat treat. Double and tripple check that the blade is straight before you put it into a tempering oven.

Doug
 
maybe i am confused on one point, you all say to double and triple check the blade before i temper but after i have HT'ed wouldnt i have been more likely to break the blade rather than bend it straight? I would have thought it would have been at its max RC after the HT and thus more brittle???

i hope i am wording that right lol
 
If we were talking about a oil or water quenching steel I would have said to make absolutely sure the steel was straight before the quench and again after. Of course if it's bent or twisted after quenching, reguardless of the quenchant, you should either reaustinize or bring it to just under an austinizing heat and straighten, confirm straightness, then austinize and quench. You could also choose to temper the blade for at least one cycle and try to straighten it before it cools. I don't have the best eye for straightness so I employ a steel straight edge as a second check. I'm just completing a large chopper forged from 1084 that I straightened out a few minor curves on the anvil with a wooden maul after tempering while it was cold. I would be reluctant to try that with a small blade made from a stainless steel. You are right, however, that you would not want to try to straighten and untempered quenched blade. Water and oil quenching steel also has the advantage that one can normalize the blade and work straightening it in a softer state.

The reason that I said to make sure that the blade is straight before tempering is I feel that that is when most blades warp, before tempering. But that's not to say that there aren't instances when the blade goes into the tempering oven straight and the knife grimlins attack and it comes out warped. I just think that if the blade is warped coming out of the tempering oven it was probably warped before it went in. It just pays to double check before putting the knife in the oven.

Doug
 
I would try bringing it back up to tempering heat while clamping the blade straight. You might also try over correcting it with clamps and shims when re-tempering. That's what I do for my 1095 blades anyhow.

What I do is take a piece of 3/8"x2" steel flat stock that's as long as the blade, and I clamp it with some little C-Clamps to the blade. If I need to over correct, I use some flat washers for shims. Works very well in my experience. You could also use some square tube, or anything else that will stay straight when heated and clamped.
 
I have the blade in the oven for another temper cycle, i will try to push out the last little bit of the bend as soon as it is done, there really isnt very much bend to it, but just enough to bug the hell out of me lol. i am just pushing the blade against my table, i will have to rig up some kind of like you said Andrew.

Ya the blade was warped when it came out of the HT, i saw it but figured in the high RC state it was in and already being cool it wasnt a good time to try to straighten it. After that i put it in the LN treat for the night, and then tempered the next morning like i have been doing and tried to bend it a bit when i got it out of the oven

Guess we will see how goes here in a bit when she is done

thanks guys

steve
 
ARCustomKnives said:
I would try bringing it back up to tempering heat while clamping the blade straight. You might also try over correcting it with clamps and shims when re-tempering. That's what I do for my 1095 blades anyhow.

What I do is take a piece of 3/8"x2" steel flat stock that's as long as the blade, and I clamp it with some little C-Clamps to the blade. If I need to over correct, I use some flat washers for shims. Works very well in my experience. You could also use some square tube, or anything else that will stay straight when heated and clamped.
Click to expand...

+1, the technique is generally known as "fixture tempering". I use a piece of flat stock as thick or a little thicker than the blade, usually bent just a hair to put a tiny counter-bend on the blade when it is clamped. I always do this after at least one complete temper cycle, bending it after quenching but before tempering is asking for disaster unless you catch it before the MF transformation right out of the quench (mostly for oil-hardening steels).
 
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