Heat treat on small 1084 blade

[n80shutterbug]

Hi guys. This might be addressed somewhere else, I didn't find it. Is the heat treat (particularly the tempering part) different for different thickness blades? I'm working with 1084, and making a small folder for a nephew's Christmas present. The blade is about 2 and a half inches long, and maybe 3/32" thick. Is the tempering times or temps different for this than say a six inch 1/8" blade?

I plan to put in the oven at 400 for an hour, let cool to room temp, and do it again. Please help if you can shed light for me, I'm a beginner at this. Also, as a folder for a young boy, I obviously don't want this to snap anytime on him, it would be better to sacrifice a little hardness than risk failure I think, so are my times and temps okay, or should I be tempering more? Thanks!

 

[Remyrw]

A particularly thick piece might need more time to get the temp to soak in completely, but that sounds fine. That's the same cycle I use on 1/8" 1080 for most of my knives and while I've bent particularly thin tips by stabbing them into wood and bending sideways I have NOT broken one yet. I've been pretty pleased with the results. You should be a bit harder with 1084, but not a lot. If you want to be conservative you could check a chart for the next step down on hardness.
Keep in mind that an oven or toaster oven is generally tempering as if slightly warmer than you're setting, a thermometer is important if you want to know where you really are. The issue is that the blade is absorbing radiant heat when the coil or burner is active and that heat is higher than the set temp. My solution is to use a tray in the toaster oven. The tray is between then heating elements (which are shielded already) and the grate that has the knife or knives. That way they tend to get a very consistent temp without being directly heated by the radiant heat coming off the heating element. This was actually the subject of a recent thread I think.

 

[Stacy E. Apelt - Bladesmith]

400 is a tad lower than I recommend. I usually go 450F for a Rc around 59.I also temper two-hour cycles, twice. I prefer the kitchen oven to a toaster oven.

Pre-heat the oven to 450, and put in the blade. Bake for two hours, take out, cool in running water to room temp, put back in for another two hours, take out and cool in running water. Finish the blade.

The quenchant and hardening methods are more of a concern than the tempering, BTW. How are you hardening the blade?

 

[n80shutterbug]

I am forging with a small coal forge. I heated the blade to non magnetic (checking with a magnet), and then brought it to just a little hotter by watching the color. I would say the color was dark red when I quenched, although I know that color is hard to judge depending on light. I was outside though not in full sun, and I basically could hardly see color, but I know if I'd been inside it would have been red. I quenched in vegetable oil. Checking it with a file immediately after, it seemed like it hardened very good. I could scratch the surface, but the file wouldn't cut it.