What is the difference between a file and a rasp?
Files and rasps are both bars of steel with teeth cut into the metal. It is
how the teeth are cut and shaped that distinguishes the file from the rasp.
Files have teeth that extend as continuous rows across the face at an angle.
Files with rows of teeth going in one direction are called mill files. Files
with rows going in both directions are called double-cut or flat files. Mill
files generally provide smoother finishes than double-cut files.
The closer the rows are to each other, the finer the cut of the file in use.
Coarse files are called bastard files. Medium files are called second-cut
files. Fine files are called smooth files.