SFM Calculator
Enter diameter and spindle RPM to calculate surface feet per minute instantly. Compare the result with HSS and carbide starting ranges.
Formula and worked example
Material SFM chart
These are typical starting ranges from the ShopCalc material library. Verify against the tool maker’s data and adjust for rigidity, engagement, coolant, and workholding.
| Material | HSS SFM | Carbide SFM |
|---|---|---|
| Aluminum 6061-T6 | 200–400 | 600–1200 |
| Aluminum 7075-T6 | 200–400 | 600–1500 |
| Brass (free-machining) | 150–300 | 500–1000 |
| Bronze (manganese) | 80–150 | 300–600 |
| Copper (pure) | 100–200 | 400–800 |
| Cast Iron (gray) | 50–90 | 200–400 |
| Ductile Iron | 50–80 | 180–350 |
| Mild Steel (1018) | 80–110 | 300–600 |
| Alloy Steel (4140) | 60–90 | 250–500 |
| Tool Steel (D2) | 30–50 | 150–300 |
| Tool Steel (H13) | 32–55 | 162–329 |
| Tool Steel (S7) | 32–55 | 162–329 |
| Tool Steel (A2) | 32–55 | 162–329 |
| Tool Steel (M1) | 30–50 | 150–300 |
| Stainless 304 | 30–60 | 150–300 |
| Stainless 316 | 30–55 | 140–280 |
| Stainless 17-4 PH | 25–50 | 120–260 |
| Titanium (Ti-6Al-4V) | 20–40 | 100–200 |
| Inconel 718 | 10–25 | 60–150 |
| Plastic (Delrin) | 300–800 | 800–2000 |
| Magnesium | 300–800 | 800–2500 |
| Nickel (pure) | 40–70 | 150–300 |
| Lead | 200–400 | 400–800 |
| Zinc | 150–300 | 400–800 |
Frequently asked questions
How do I calculate SFM from RPM?
Multiply diameter in inches by RPM and pi, then divide by 12. Use the cutter diameter for milling and the workpiece diameter at the cutting point for turning. SFM is surface feet per minute; SFPM is another abbreviation for the same quantity.
What SFM should I use for titanium?
For Ti-6Al-4V, the ShopCalc starting range is 20–40 SFM with HSS and 100–200 SFM with carbide. Tool geometry, radial engagement, coolant delivery, machine rigidity, and the tool maker’s recommendation can all justify a lower or higher value.
Does the same SFM formula work for a lathe?
Yes. The surface-speed relationship is the same for milling and turning. On a lathe, use the current workpiece diameter where the insert is cutting. As a facing cut approaches center, constant-surface-speed control raises RPM to maintain the selected SFM.
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