Tracey Cheuvront Posted February 11, 2022 Share Posted February 11, 2022 I’ve been making woodworking tools at a small scale for over ten years and have mostly been successful achieving good to excellent edge retention on axes, adzes, chisels, spokeshaves, and drawknives. I always use the same basic heat treat: heat to just past non-magnetic with a charcoal forge or propane torch, quench in canola oil, temper at 400F for two hours. I use mostly unknown steels, so any time a tool wouldn’t take a good temper, I chalked it up to that. No biggie, most turn out great. Suddenly, none of my drawknives will harden properly, even using known 1080 and 1095. I’m a professional woodworker, have restored and used scores of antique drawknives, and can fairly say that some of the ones I’ve made hold an edge as well as or better than even the best vintage ones. Before becoming a woodworker and toolmaker, I was a technician in a biology research lab where even the tiniest deviation from protocol could ruin an experiment, so I’m meticulous and detail oriented in my process, simple though it is, and try to be as consistent as possible. I’ve changed out my quench oil, tried quenching edge-first vs. spine-first, with the oil at 50F vs 135F, even tried quenching some in water instead of oil and they still won’t harden. I mean, 1/8” to 3/16” 1080 and 1095 should not cut easily with a file straight out of a water quench, right? I also tried grinding off an extra several thousandths from the back and the bevel in case of surface decarb. But here’s the most bizarre thing. If I make a chisel from the exact same piece of bar stock and do the exact same heat treat, the steel hardens properly and holds an edge. And, one of the best drawknives I ever made came from a piece of bar stock that is now not hardening. Could it possibly have something to do with the fact that I arc-weld the blade steel to the mild steel frame? Because it seems it’s just the blades that get welded that don’t harden. This doesn’t seem right to me since it has worked fine many times in the past, the edge is an inch or more away from the weld, and I do the weld before heat treat when the blade steel is factory annealed. This has happened on a dozen drawknives in a row now, most of which I have attempted to heat treat more than once, all to no avail. I’ve spent two solid weeks of shop time trying to figure this problem out and it just keeps getting more mystifying and discouraging. Any insights or suggestions would be dearly appreciated! And if anyone out there has professional equipment and could normalize and heat treat a small batch of drawknives for me, please let me know what you would charge for that service. Thanks! Link to comment Share on other sites More sharing options...
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