Surface speed (SFM) is how fast the cutting edge travels past the work. Solve it from a known RPM and diameter to compare a setup against recommended speeds for the material.
SFM = (RPM × π × D) / 12 ≈ RPM × D / 3.82
What the variables mean
| Symbol | Meaning |
|---|---|
| SFM | Cutting speed (surface feet per minute) |
| RPM | Spindle speed |
| D | Cutter or part diameter (inches) |
Worked example
A 0.5 in tool at 2,292 RPM: SFM = 2292 × 0.5 / 3.82 = 300 SFM.
Skip the arithmetic with the Surface Speed (SFM) calculator in Feeds & Speeds.