AEB-L blade warping during post heat treat grind

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FatFrumos

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May 7, 2018
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Hello. I know there are numerous threads on Aeb-L warping during the HT process. I have not had this problem, they come out of cryo dead straight. However, as I started grinding my bevels (it's a kitchen knife), I noticed that it developed a slight warp on one side. Now, knowing about the tendency of this steel to warp I was very careful about keeping it cool - dunking it in water after every pass, spraying water on my belt. Yet, there is a warp. So I guess my question is, does it warp because of the temperature changes during grinding or because it has some stresses in it. Usually I would say from stresses, but I just finished another kitchen knife from the same chunk of steel and it ended up being straight.

I've seen one guy on forged in fire fix a warp by pouring a cold water on one side of the blade while it was still hot. Im going to try it today, not sure it'll help, but if anyone has any tips on how to keep the blade straight after HT, I'd really appreciate them.

Thank you!
Luka
 
I try to grind thin AEBL kitchen knives evenly on each side as I work towards the spine opposed to taking an entire side off then switching sides. You will normally find it warps towards the side that has been ground down more and will even out as you grind the other side. Just my experience.
 
I think it warps because you are relieving residual stresses. Keeping the grind even between the two sides helps. Some people have suggested that a sub-critical anneal reduces warp later on, but unfortunately, that has not really done much for me. In my experience, AEB-L does not respond to straightening during tempering. The best method I have found is to use a carbide tipped hammer. I made one out of an old ball peen hammer and a piece of 1/4" carbide from McMaster. To shape the carbide, I spun it in the drill press and used a rotary tool with a small diamond disk.

The thinner the AEB-L, the more warping issues I get. I just finished a petty knife out of 0.06" thick AEB-L that I had to straighten a couple of times during grinding. If find it's better to not use a lot of force when peening, but rather peen more often. That makes it a lot easier to grind or sand away the peening marks without introducing another warp.

There also seems to be a good bit of variation between AEB-L orders I have placed. I have had some batches that all came out of heat treating straight as an arrow, others turn into bananas. If you have not had any issues so far, I think you got lucky.
 
I stopped using AEBL for slipjoints due to a couple of blades warping after heat treat from grinding.
 
ChristoDart said:
I try to grind thin AEBL kitchen knives evenly on each side as I work towards the spine opposed to taking an entire side off then switching sides. You will normally find it warps towards the side that has been ground down more and will even out as you grind the other side. Just my experience.
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It does correspond to my observations - I did spend a bit more time on the side it warps towards. I'll try to do the other side today, thank you!
 
Hubert S. said:
I think it warps because you are relieving residual stresses. Keeping the grind even between the two sides helps. Some people have suggested that a sub-critical anneal reduces warp later on, but unfortunately, that has not really done much for me. In my experience, AEB-L does not respond to straightening during tempering. The best method I have found is to use a carbide tipped hammer. I made one out of an old ball peen hammer and a piece of 1/4" carbide from McMaster. To shape the carbide, I spun it in the drill press and used a rotary tool with a small diamond disk.

The thinner the AEB-L, the more warping issues I get. I just finished a petty knife out of 0.06" thick AEB-L that I had to straighten a couple of times during grinding. If find it's better to not use a lot of force when peening, but rather peen more often. That makes it a lot easier to grind or sand away the peening marks without introducing another warp.

There also seems to be a good bit of variation between AEB-L orders I have placed. I have had some batches that all came out of heat treating straight as an arrow, others turn into bananas. If you have not had any issues so far, I think you got lucky.
Click to expand...
How do you use a carbide-tipped hammer? Is there a good video on the subject matter? Thank you!
 
FatFrumos said:
How do you use a carbide-tipped hammer? Is there a good video on the subject matter? Thank you!
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The guy I bought mine from said to strike the concave side of the blade in a line straight down from the spine to the edge. Sorry, that's all I got.
 
FatFrumos said:
How do you use a carbide-tipped hammer? Is there a good video on the subject matter? Thank you!
Click to expand...
There is a Murray Carter video on youtube about blade straightening methods that includes straightening with a carbide hammer. I think it is the one below, but I don't have time to go through it at the moment to check.

 
Can confirm carbide tipped hammer. A lot of light hits/marks and multiply times through grinsing. Keep away from the edges and dont hit hard, I cracked two blades.
 
I just made a carbide tipped hammer this past week. Took an old carbide drill bit, drilled into an old hammer with the bit. Snapped the carbide bit off (the fluted section), shaped it down and then stuck it into the hole in the hammer face. Didn't even need to use glue/epoxy! I used an old hammer with a ball pein end and a flat end, it is fairly light weight (lighter than a regular hammer) and I just let the hammer fall onto the blade with it's weight alone and it seemed to work pretty well.
 
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