Norton Taper Triangle File Stone 4" x 1/2" x 1/4". Triangular Files are used for a variety of deburring, chamfering & radiusing applications including cleaning tap threads, stoning cutting surfaces of milling cutters, lapping honing tools, dies & molds, & putting precision points on center punches. Tapered Triangles, used by mechanics and tool and die makers to impart the correct edge in the least time. To improve sharpening & reduce clogging, use with oil. Composed of an aluminum oxide abrasive. Oilstone made by Norton, Saint Gobain. Model FF544 .