How do you calculate feed rate on a lathe?

• A. Speed × time
• B. Depth of cut × width of cut
• C. Torque × RPM
• D. RPM × feed per revolution

Answer: (D)

Feed rate is the distance the cutting tool advances along the work per minute. The best way to get it is to multiply how far the tool moves for each spindle revolution (feed per revolution) by how many revolutions occur each minute (RPM). So, feed rate = feed per revolution × RPM. For example, if you have a feed per revolution of 0.005 inches and the spindle runs at 600 RPM, the feed rate is 3.0 inches per minute. This is what you use to predict how quickly the tool moves and to estimate machining time. The other ideas don’t represent the actual axial advance: combining speed and time yields a distance but not the controlled per-rev advance; depth of cut and width of cut describe material removed per pass, not the tool’s axial feed; torque × RPM gives power, not feed.