Spindle Speed Chart
This spindle speed chart converts common SFM values into RPM for common cutter and drill diameters. It is useful for milling machine speed charts, drill RPM charts, and manual-machine setup.
SFM to RPM chart
| SFM | 0.125" dia | 0.25" dia | 0.375" dia | 0.5" dia | 0.75" dia | 1" dia |
|---|---|---|---|---|---|---|
| 50 | 1528 | 764 | 509 | 382 | 255 | 191 |
| 100 | 3056 | 1528 | 1019 | 764 | 509 | 382 |
| 150 | 4584 | 2292 | 1528 | 1146 | 764 | 573 |
| 200 | 6112 | 3056 | 2037 | 1528 | 1019 | 764 |
| 300 | 9168 | 4584 | 3056 | 2292 | 1528 | 1146 |
| 500 | 15280 | 7640 | 5093 | 3820 | 2547 | 1910 |
| 800 | 24448 | 12224 | 8149 | 6112 | 4075 | 3056 |
| 1000 | 30560 | 15280 | 10187 | 7640 | 5093 | 3820 |
| 1500 | 45840 | 22920 | 15280 | 11460 | 7640 | 5730 |
SFM to spindle speed calculator
Reading the RPM chart
Find the SFM row and tool diameter column. If the recommended RPM exceeds the machine limit, use the maximum safe RPM and recalculate feed from actual RPM.
FAQ
Are these chart values final production recommendations?
No. They are starting values for planning. Use the specific cutting tool manufacturer data, workholding condition, coolant method, and machine limits before running production parts.
Why do different speed and feed charts disagree?
Charts assume different tool materials, coatings, tool life targets, rigidity, coolant, radial engagement, and material hardness. A generic chart should be adjusted to the actual tool and setup.
How do I convert SFM to RPM?
For inch units, RPM = 3.82 × SFM ÷ cutter diameter in inches. For metric units, RPM = 1000 × Vc ÷ (π × diameter in millimeters).
Why does a smaller tool need higher RPM?
At the same surface speed, a smaller circumference travels less distance per revolution, so it needs more revolutions per minute to reach the same cutting speed.
Data sources and limits
These charts are starting values only. Actual speeds and feeds depend on tool geometry, coating, holder rigidity, coolant, chip evacuation, radial width of cut, axial depth of cut, material hardness, and machine power.
- Sandvik Coromant: milling definitions for cutting speed, spindle speed, feed per tooth, feed per minute, MRR, cutting force, and power.
- Kennametal: RPM, IPM, chip-load, and SFM formulas.
- Harvey Tool: general carbide end mill SFM and chip-load tables.
- Norseman Drill & Tool: HSS drill speed and feed rules of thumb.
- LittleMachineShop: turning, milling, drilling, and reaming cutting speed tables.