Warp happens. I can usually correct warp by clamping past straight and running another temper cycle at 25 degrees higher than the previous cycle. Most of the time on a carbon steel blade I can do the clamping between the first and second temper cycles and get them straight fairly easily. Rarely a carbon knife will take a third temper cycle to get straight.
I've got a batch of eleven CM154 knives that are giving me eternal fits. Some are 3/32, some are 3/16, all have thin tapered tangs and bevels ground. The problem started when I put more blades in the oven rack than would fit, so some of them leaned over sideways instead of sitting upright. The combination of gravity and austentization temp put a bow in most of the blades during the soak. I plate quenched them all, hoping that the plates could get the blades back straight. I also used welding gloves and hand straightened all the blades as they came off the plates. They were all fairly straight by the time I put them in the dry ice/kerosene.
After dry ice overnight, the warp was back. Most of them had returned back to bowed, even after I had hand straightened them. I ran the first temper cycle at 450, so I'd have room to work up to a final temper cycle of around 550.
Since then, I've run some of the blades through tempers with clamps at least four times. They won't move consistently, even at higher tempering temps. Eventually with the combination of increased temps and clamps, I was able to get 6 of them straight. I was able to get the blades straight then use a torch to heat the handle and straighten a few more manually. I've still got 2 that are crooked.
What could I have done differently? What should I do next time to avoid all this?
Any suggestions on what to do with the crooked blades? Keep trying, or re-heat treat, or scrap?
I've got a batch of eleven CM154 knives that are giving me eternal fits. Some are 3/32, some are 3/16, all have thin tapered tangs and bevels ground. The problem started when I put more blades in the oven rack than would fit, so some of them leaned over sideways instead of sitting upright. The combination of gravity and austentization temp put a bow in most of the blades during the soak. I plate quenched them all, hoping that the plates could get the blades back straight. I also used welding gloves and hand straightened all the blades as they came off the plates. They were all fairly straight by the time I put them in the dry ice/kerosene.
After dry ice overnight, the warp was back. Most of them had returned back to bowed, even after I had hand straightened them. I ran the first temper cycle at 450, so I'd have room to work up to a final temper cycle of around 550.
Since then, I've run some of the blades through tempers with clamps at least four times. They won't move consistently, even at higher tempering temps. Eventually with the combination of increased temps and clamps, I was able to get 6 of them straight. I was able to get the blades straight then use a torch to heat the handle and straighten a few more manually. I've still got 2 that are crooked.
What could I have done differently? What should I do next time to avoid all this?
Any suggestions on what to do with the crooked blades? Keep trying, or re-heat treat, or scrap?
