When filing in a lathe, don’t hold the file rigid, but use a slight gliding motion. This will help the file clear itself and also prevent ridges. When filing metal, vary the speed according to metal. Generally use 150 surface feet per minute for cast iron; 175 for annealed tool steel; 350 for machinery steel, and 500 for soft yellow brass. Also, don’t run your hand over the work. Resulting oil and moisture will make it harder for the file to take hold.