Just a passing thought: Wouldn’t a modified sewing machine work
wonderfully as a mechanical FILE rather than as a saw? Just remove the
bobbin mechanism and enlarge the sewing needle clamp to accept a
needle file, break off the file’s tip (most worn out needle files are
still useful at the back anyway) shorten the tang and you’d be able to
file with nearly perfect vertical edges. It wouldn’t take much
modification at all.