Always select the proper blade for work to be done. The main danger in using a hack saw is blade breakage, always use proper pressure. D. Files 1. Files are graded according to their degree of fineness and whether they have single or double-cut teeth. Files are useful for removing small amounts of metal, plastic or wood and are used extensively in tool sharpening.
Files come in different shapes.
Round f. Flat 3. A new file should be broken in carefully by using it first on brass, bronze, or smooth cast iron. Protect file's teeth by hanging it in a rack when not in use. Avoid getting files oily. Do not strike a file against the bench or vise - use a file card to clean it.