The app calculates RPM for lathe depending on material and its designation. How to use: 1. Select material, 2. Select designation, 3. Select Tool type, 4. Optionally change measurement units, 5. Enter work diameter. The app will calculate the RPM value. The following materials are supported: - Structural steel, - Plain carbon steels, - Resulfurized plain carbon steel, - Leaded plain carbon steels, - Resulfurized alloy steels, - Water hardening tool steel, - Cold work, oil hardening tool steel, - Cold work, air hardening tool steel, - Stainless steels (Austenitic), - Cast Iron, - Brass, - Bronze, - Copper, - Wrought aluminum, - Cast aluminum, - Machinable Wax, - Acetal Copolymer (Delrin), - Polyethylene, - Acrylic (with coolant), - Polycarbonate, - Teflon, - Nylon/Acetal, - Bakelite, - Hard rubber, - Wood. If you have any suggestions please let us know.