I started the finish work on the demo-axe-head, but it was really too hot to do much forging. I drank half a gallon of water, banged on metal for an hour, then drank another half gallon and decided to take a break. I'll try again this evening if/when it cools down a bit.
The work today consisted of taking the now-annealed axe head and doing the primary grinding on it. Since the edge only has steel on one side of the blade, I only removed a bit of metal on that side -- just enough to get through any decarburization that may have occured. Decarb is where the steel is heated in an oxidizing environment, and the carbon (remember, carbon is what lets steel get hard) gets burnt out. Between the forge-welding and forging to shape of the edge, this could be quite a thick layer, so I removed about 1/16" from the edge, and removed about 15/1000" from the side of the edge with the steel on it, giving me what should be a decarb-free edge. I then ground in about a 20 degree bevel on the other side. This results in a steel edge backed by the iron body of the axe, very tough and hard when heat treated properly.
Speaking of which, now that I had the axe ground to withing a few 100ths of an inch to where I wanted it, I put it in the pre-heated but turned off forge. I spent some time forging the other axe head first, so the forge was glowing a merry orange even without the gas turned on. With the lights turned out and the doors closed, I could judge the temperature fairly well, so didn't bother with the heat treat oven. After a few minutes, it was at the proper temperature, which I checked with a magnet (the curie point, or point at which iron loses its magnetism, is generally about 50 deg F lower than the critical point.) Since
1050 is a relatively low-carbon steel (though technically considered a "high carbon" steel) I quenched in water. A check with a file revealed that I had, indeed, managed to harden the edge.
To temper, I used a torch and heated along the back of the edge of the axe. Watching the colors, I heated until it started to turn purple then quenched. This will give a tough, springy edge, still hard enough to hold a good edge, yet tough enough to withstand the abuse that an axe will go through. A quick sharpening to bring the edge to a shaving sharpeness, and the axe head is done.
To test, I mounted it on a spare hammer handle I had around, then attacked a chunk of cherry limb I had in the shop. It cut quite well, and didn't chip or dull despite cutting through a rather tough knot in the wood. I've now taken the axe handles I'm making out of the stabilizing chamber, so once they dry I'll go ahead and mount and finish this one off.
I'm leaving the oxide and scale on the blade, as well as the oxidation colors from the heat treatment, as I view this as a primitive, "as they would have made it" type of axe. Sure, I could have ground, filed, sanded, and polished it to mirror-like perfection, or even blued or put a decorative finish on it, but that's not the point. this is a quite functional axe, very much like some I've seen in books on ancient arms, made with a minimum of materials. It's certainly nothing I'd like to get hit with, and is both practical, and if I must be the only one who says so, quite pretty to look at. Pictures coming up in a couple of days (if I can get this camera to work right.)