The first couple I made I used a cold chisel to score the circular saw blade and broke out the rough points. Then used a file to shape, clean up and sharpen.
A 2 1/2"x1" triangle with a slot on either side or holes drilled on either side for securing with a wrap works well.

Do some more searches.  From what I have read, you can do heat treating of the broadheads using first your torch  and then your oven.

Good luck
ChuckC

I am not knocking what others are saying but dont over think the whole tempering thing. If you run your file down the blade and metal comes off really easy then the steel may be a little soft and wont hold a good edge, and may bend easliy. If you run your file down the point to sharpen and no filings come off well its to hard you cant sharpen in the field. I have soften too hard a point by heating and then just sticking in sand to cool and after completely cooling I then could get shavings off with file. Not very scientific but effective. The 02 tool steel I have used comes pretty hard, after cutting out with dremmel which heats up the steel, and grinding in my bevels which heats up the steel, I still find them a good hard steel that I can sharpen with file and hold a good edge. Old saw blades are softer but still hold a pretty good edge and are durable. I have only bent one so far on a miss that struck some very rocky ground. No head that I have shot into an animal has bent on bone.