Tempering to 350F should get it to about Rc62. 400F will yield about Rc60 -- still plenty hard for most purposes but Rc62 will hold an edge a bit longer. 2 hours is way more than enough but there is no harm in holding at temperature for that long.

@@HockTools thank you. So, it seems preferable to put the iron into the oven at 350F and let it ride for how many minutes (if we do not want to risk messing up with the straw coloured propane gas reheat/quench)?

@@LitoGeorge If you trust your oven to not exceed the set temperature you can leave it in there almost indefinitely. The "rules" say to soak for twenty minutes per inch of cross section so with our thin blades and knives, just be sure it's reached the target, let it soak for a few minutes or more and you should be good to go. If you find it's too brittle, toss it back in to, say, 375 or 400 for another soak.

@@HockTools excellent, thank you. I have just heat treated 3 plane irons from the 1850's to 1890's. I'll be tempering them in the next hour. How would I test for brittleness (ie: too brittle?) Thank you.

@@LitoGeorge Take them for a test drive in some hard wood to see how they perform. If they seem too brittle you can re-temper to a higher temperature.

The Martensite forms when the Austenite is cooled rapidly during the quenching.

@@robc2536 Thank you Ron....so you end up with Martensite

Yes. Martensite is the desired end product crystal structure of heat treatment. (Thanks, Rob C!)

Hi Gerald! How nice to hear from you. Have you used up that blade yet? We have more, you know.

@@HockTools That plane iron is nearly gone and I have been thinking about buying some more. The good thing is I have several and rotate them. That way I can change the blade and use a sharp one rather than taking to time to sharpen it at that particular time. When I try to explain to someone how much difference there is in the irons yoiu make, they are always skeptical until I show them the results. Then so often the response is the same---wow! There were a couple of things I noticed immediately when I used the first iron I bought from you. They were the finish I could produce and how much easier the handplane pushed. It is hard to beat results. I am glad you make them, so I can do woodworking and have the best possible success.