The quench is important, use salt brine made in this way:

1. Mix 13 ounces of common salt to a gallon of fresh water. This makes a 9 percent salt brine.
2. Keep your brine cool or at room temperature.
3. Don't quench file steel in oil. It won't harden well at all.
4. How you dunk it in the quench is equally important. If you belly flop it in it is guaranteed to warp. and may crack too. Instead plunge it straight into the brine. Move the knife in a figure 8 pattern while it bubbles, remove while still warm and temper as soon as possible.
5. Try tempering at 500, then see it is too hard. If it is temper again at 600. You can use an oven for this if you get all the grease and oil off and have a sympathetic spouse.
6. If the blade is crooked temper first before trying to straighten. Then heat to 300-400 and straighten while hot.

Rasps are another animal. They are case hardened but under this layer are fairly soft. Rasps are worthless for edge holding tools but great for throwing knives, which don't need a great edge but must be tough so they don't break. Temper these at 700 degrees.