I've made about 30 knives from files. First anealed the steel (normalised), heat the steel until a magnet will not stick, then burry them in sand to cool (it lets the steel cool slow). Iuse 3-4inches around each file. Grind your pattern, do not turn the steel blue or you will have to aneal again.Only grind close to your final size,you will fine tune after temper. Once you have the pattern you want,heat the blade until a magnet will not stick, quench in 100 deg oil,(I used old jet aircraft oil,I am an aircraft mech)I don't think type matters. Then I use an old toaster oven,heat to 400 deg,(I get about 58-59 rockwel C scale). Now finish your blade, grind and sand to your hearts desire. If you have any questions PM me, I will be happy to help in any way I can. If I get a chance I will post some pics.
Mike