1. Grind teeth of file if possible.(heat stress risers)
2. Forge to shape.(red to orange)
3. Normalize. heat steal until it is non-magnetic.
4. Forge cool.
5. Heat until not magnetic- raise 50 deg F.-hold 5 min.
6. Edge quench in oil-goop (check edge-file should skate)
7. Draw 1 hr. 400 deg F., air cool
8. Draw 1 hr., air cool.
However it depends on the steel but this should work with adequate results.