Surface Velocity Fundamentals
Velocità di Taglio (Vc) e SFM Spiegati
Cutting speed describes the linear distance passing the tool edge per unit time. Understand how tool coatings, substrate hardness, and thermal conductivity influence recommended SFM in holemaking.
1. What is SFM?
Surface Feet per Minute (SFM) represents the number of linear feet of workpiece material that passes the cutting edge of a rotating tool in one minute. If you wrapped a string around the drill’s outer diameter and unrolled it for one minute of rotation, the length of that string in feet would equal the SFM.
Imperial SFM Formula:
SFM = (π × Diameter in inches × RPM) / 12
SFM ≈ (0.2618 × D × RPM)
Metric Vc Formula:
Vc (m/min) = (π × Diameter in mm × RPM) / 1000
Vc ≈ (0.00314 × D × RPM)
2. Typical Surface Speeds by Tool Substrate
| Material | HSS (SFM / m/min) | Cobalt M42 | Solid Carbide |
|---|---|---|---|
| Aluminum 6061-T6 | 250 SFM (75 m/min) | 350 SFM (105 m/min) | 700+ SFM (220 m/min) |
| Mild Steel (1018) | 100 SFM (30 m/min) | 130 SFM (40 m/min) | 350 SFM (110 m/min) |
| Alloy Steel (4140) | 65 SFM (20 m/min) | 90 SFM (27 m/min) | 280 SFM (85 m/min) |
| Stainless Steel (304) | 45 SFM (14 m/min) | 65 SFM (20 m/min) | 180 SFM (55 m/min) |
| Titanium (Ti-6Al-4V) | 30 SFM (9 m/min) | 45 SFM (14 m/min) | 115 SFM (35 m/min) |
Solve SFM ⇄ Spindle RPM Online
Bidirectional calculation with Machine Reality spindle RPM clipping and power estimates.