I have engraved a couple. Be Careful of about 1/2" to 3/4" from the edge, a lot are differentially hardened. The edge is hard but the main body is still engravable.Running a line into the hardened part is dicey.
some were made with a rather softer steel. a wedge of hardened steel was welded in the area of the cutting edge and tempered. i used to do work for a hawk maker. that is how he did his
Question: do you think trying to soften/anneal each side of the mid-carbon steel (1045 or 1055) axe with a MAP torch until around orange or 1500 deg. Fahrenheit would be sufficient to make the sides soft enough for at least the top layers to be engraved OR do you think I would need to soak the entire axe head in the forge to anneal/normalize the whole thing?
If the whole thing needs to be soaked, then of course the edge will lose its hardness/temper, and I'll have to re-harden and quench at least the edge.
But am thinking if I torch directly the areas to be engraved it might, due to the mass of the axe head, not affect the heat treat on the edge (or at least if it does, I would then just heat and harden the edge).
Most commercial axes are castings. They sharpen easily with a file. They aren't hard like a knife blade, and certainly not as hard as some guns that guys engrave. Quit obsessing over non-existent details. Just buy one, polish it, and engrave it.
If you want to have a soft body and a hard edge, do like the Japanese sword makers do, cover everything you don’t want hardened with a clay type base and temper the exposed edge. Of course its more involved than just covering and tempering, so this is just a suggestion.
AO84. First let me say I'm a wanne be bladesmith who's still trying to wrap my head around this engraving. Your idea of drawing back any temper behind the blade edge is feasible. Support the head in a pan of water with the entire edge submerged. I don't know the exact debt as your design and the head edge style will dictate that. Personally I'd want to leave at least 3/4 to 1inch depth of tempered area behind my edge.
Additionaly you dont need to take it all the way to orange heat with the MAP. A deep battleship gray should suffice.