I heat treated 4 knives on the weekend all in 0.1" AEBL. I did something different that seemed to work. 1. I drilled and taped 4 holes in my quench plates. They're 1" thick by 15" by 4" aluminum. 2. The knife goes in the plates and are squeezed by a wood working vice. 3. I use an impact to crank down the bolts. 4. Now that everything is tight I move the plates to a bucket of ice water for a few minutes. 5. Then I removed the knives from the plates and cut them out of the foil. 6. Into the liquid nitrogen. Every single knife came out dead straight. I have always had some bend to deal with. The knives were all 7" chefs 0.1" thick. I used to use compressed air when in the vice but this was way better.