I got a great big file this week I want to use to make a razor out of. But of course the file is still hardened. Who can help me with what temperatures I need to get it soft enough to work with and for how long it would need to be at that temp?

And after softening and working the metal, what would the best temps be to harden again and what process? Oil cooling, air, water etc?

I can use a professional grade heating oven to heat so it's down to the degree and minute precise if needed.

Who could help me with some hard needed advise

Thanks.