Hot Filing

by Albin Drzewianowski

In addition to being easier to hammer when steel is hot, It is also easier to file. However, filing on hot metal can and will damage the file, it will eventually draw the temper and soften the file. So the solution is to have a special file that is only used for hot filing. How long it lasts will depend on how you use it and how hot the steel is when you file.

My "hot file" is specially marked so that I won't confuse it with my good files. Generally, the filing is done at a black heat, not a red hot or hotter temperature. You can file at the higher temperatures, but the file just won't last as long. You want a large, coarse file, commonly know as a bastard cut. A fine tooth file will not take off much metal and because the file teeth are so much thinner, they will lose their temper much faster.

One of the common uses for hot filing, is after hot cutting. I give both ends that have been cut a couple of quick passes with the hot file to take off any burrs left by the hardy or hot cut. (As a general rule, no matter how you cut the steel: Chop saw, hack saw, cut-off hardy, etc., always dress both ends of the cut, so you don't end up with a jagged edge that can cut you or some other unsuspecting person in the shop.)

You want to be especially careful while hot filing, as your hands come in close proximity to the hot steel. Take long strokes, use the entire length of the file. Lift the file off of the steel on the return stroke; as with any filing, don't drag the file back across the steel, that is a bad habit, whether filing hot or cold steel.

I have found that used horseshoe rasps really work well for this function. If you happen to know a farrier, they are easy to come by. Plus you frquently see them in the Iron-In-The-Hat. One side is a rasp the other side is a coarse file. It is a large file and really can take off some metal. Once you start to notice that it is no longer removing metal, you can then use the file for raw material in some project, a snke, knife, etc.

If I find that I need to use my "good" files, I always make sure that the metal is cool to the touch, so that I don't risk damaging the file.

-- RebStaup - 25 Jan 2008