Originally Posted by DIY_guy

You wont be able to anneal it with the handle on (that you show in the first picture). Most old files are made from WI steel (W indicates water quench) but it could even be 1095 steel.

You could bake the file in the oven at 450/500 Degrees F and then turn the oven down to 400 for an hour and then 300 for a half hour and then leave it in the oven to slowly cool. That will soften it up a but allowing you to grind a bevel, drill holes and do final shaping.

Then your going to need to re-harden and temper the steel so it holds an edge.

Heat the blade to 1,400-1,500 degrees F (A magnet should not cling to the metal at this point) Then quench the steel in 180 Degree F salt water or veg oil. Have your oven preheated to 450 degrees F and take the still hot blade and temper it for an hour in the oven.

Its going to look black and scaley so you will need to clean it up and polish it again.

After this, get your hands on some O1 tool steel (buy it already annealed) and save yourself some work.