Surface Finish Calculator FAQs
Surface speed is the rate at which the workpiece surface moves past the cutting edge at the point of contact. In turning operations, the cutting tool is stationary and the workpiece rotates. This means surface speed is based on how fast the outer surface of the spinning part moves past the fixed cutting edge. It is used to calculate spindle speed (RPM) and directly impacts tool life, heat and surface finish.
Theoretical surface finish is calculated using feed rate (IPR) and tool nose radius, which determine the roughness left by the cutting tool. In general, larger nose radii and lower feed (IPR) result in better surface finish. Kennametal's turning surface finish calculator combines these variables to help you quickly identify the optimal starting parameters for your application.
Actual surface finish will deviate from theoretical values due to:
- Cutting speed (SFM) and thermal effects
- Tool wear and edge condition
- Built-up edge (BUE) formation
- Machine rigidity and chatter
- Material properties
Calculating surface footage or surface feet per minute (SFM) requires consideration of your cutting tool’s diameter and spindle speed. After multiplying diameter by spindle speed, divide by 3.82 (the industry standard).