Special files are rather easy to make for a special purpose. Thinking back about hand saws, the rip saw and cross cut saw. These were sharpened, and even the teeth were set by carpenters of the past, There were special vises that were designed to hold the saw blade for filing. The key was the saws were made (I am assuming) out of a medium carbon steel, were were "spring tempered" so they had toughness to retain the edge but also could be filed to sharpen.
You can made a special purpose file out of an old file, anneal the file, cut the teeth with a tree corner file before hardening and tempering. Now it can be sharpened like the crosscut saw when it needs it. After hardening and tempering lightly sharpen to get the edge back. The extra narrow pillar file, about 5/16 by 1/8 is in a shape to make a special file. Obviously, these are wood cutting saws, I mean files.
