Warped blade in 5160 - questions

J

Jorcheim

Member
Hey guys. Been a lurker and infrequent poster for a few years now. Starting to get serious about knifemaking (finally), and I had a question about warped blades. I'm not a fulltimer, and I'm only producing a couple of blades a week at this point, so I have a little more time to dedicate to each blade. I'm using solely 5160 at this point. My question is this. If after quenching I have a warped blade, rather than trying to straighten immediately post-quench (around 500 deg F), why not just renormalize, then straighten under heat, then reanneal, starting the entire ht process over again? Sure, it's time consuming, but from a metalurgical and end product standpoint, is there anything functionally wrong with that approach?

So just to be clear, what I'm suggesting for input is the following:

Step 1: Renormalize
Step 2: Straighten in vise while still hot (is 500 deg F sufficient?)
Step 3: Start entire ht process over

Just to be clear, I tend to use a version of Ed Caffrey's ht recipe, if that helps.

Thanks in advance, guys. Any assistance would be much appreciated.
 
I don't think there is anything wrong with doing what you suggest. Other than the added chance of ruining a blade during the quench. I have had pretty good success taking the warp out in the tempering cycles. Why reheat treat if you don't have to. Just my preference saves a little time and expense.
 
It's WAY easier to just straighten it during one of the temper cycles. I don't know why you would want to go through the whole process over.......even if it doesn't hurt anything. It's so easy to just do it during the tempering if you miss your chance to do it during the end of the cooling after the quench.
 
Metallurgically, extra decarburization, scale and the undoing of all the good things, as far as refinement, you may have done in all the previous treatment. You may be able to get the latter all back to where it was but it will take a lot of unnecessary time and effort that will add to the decarb and scale. If it got passed me in the quench, I would just straighten during tempering. If that didn't work, and I have yet to seen one that it didn't, then I may consider a simple stress relieving and re-hardening, but only of it was one special blade, otherwise I would be tempted to scrap it and grab another blade as I would always have a feeling about a blade that resisted all those efforts to stay straight.
 
Hey guys, just wanted to give you an update. I finally got around to working on that knifeblade, and after re-normalizing and re-annealing it three times, it's pretty much dead nuts post-quench. I used a 3-point clamping process to straighten, and the vise to correct the slight twist. I will be posting pictures very soon. Thanks for the advice. Much appreciated.
 
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