Sorry Ohio, but to use an overused expression, "with all due respect", that is not really, truly, quite the best advice.
It is not best, or necessary to anneal a file in that manner. Bring it up bright red/red-orange and let it cool will allow it to be drilled or filed. Bring it up to a very dull red half a dozen times seems be even better. Colors are seen differently by different folks. One shade of red, or heat color, beyond non-magnetic is the target heat for the quench for a hypereutectic carbon steel, and should be close to 1475°, give or take a bit. Light oil is correct, but it needs to be heated to about 125°, and canola oil would be the best as far as cheap and easy to get appropriate oils. Once into the quench, the blade should be moved fore and aft, but never sideways. Point down into the quench causes less warp. The temper for a file blade can be as high as 500°, but not much more, as it is possible to cause the steel to become brittle in the 600° range. This problem begins in the mid to low 400°'s range, so it is best to not push the temp too far over that. Two one hour tempers at 450° should be very sufficient, and quench in water after each temper heat. Lead melts at 625°, not 740°, which in fact is a good temper heat for springs. A little much for most knife purposes. Again, sorry to correct you, but your info really needed a wee bit of adjustment.