WIDIA™ VariTurn Grade Numbering System A system of grades, geometries, and application guidelines to provide optimal solutions for your metalcutting needs. It’s easy to determine which WIDIA™ chip-control cutting tool will work best in your specific workpiece materials and applications! TN 15 M Brand Relative Hardness Primary (ISO 513) Workpiece Material (ISO 513) TN = WIDIA 01 = Hardest P Steel 10 M Stainless Steel 20 K Cast Iron 30 N Non-Ferrous 40 S High-Temp Alloys 50 = Toughest H Hardened Materials U Universal Machining B110 widia.com