Crescent® Nicholson 8" x 3/16" Round Smooth Chain Saw File is a black diamond, spiral cut, American pattern file. The spiral cut enables more material to be removed with each stroke, reducing the amount of strokes to produce a keen edge. It is carded. Straight tang. File from inside to outside of cutter. Place file against beveled cutting surface of teeth 20 degree to 45 degree with saw. Sharpen all left hand cutters on one side of chain then move to the other side and file all the right hand cutters. Height between cutting teeth and depth gauge is between 0.020 to 0.030 inch.