Use this chart as a starting point for setting spindle speed and feed rate on a mill. Pick a cutting speed (SFM) for your material and tool, convert it to RPM for your cutter diameter, then set feed from the chip load per tooth. Plug the numbers straight into the Feeds & Speeds calculators to do the arithmetic.
RPM = (SFM × 3.82) / cutter diameter (in)
Feed rate (IPM) = RPM × chip load (in) × number of flutes
Cutting speeds (SFM) by material
Surface feet per minute for milling. Carbide runs several times faster than HSS. Start near the low end of the range and increase once the cut proves stable.
| Material | HSS tool (SFM) | Carbide tool (SFM) |
|---|---|---|
| Aluminum (6061, 7075) | 250 – 300 | 600 – 1200 |
| Brass (free-machining) | 150 – 250 | 400 – 700 |
| Bronze | 100 – 150 | 300 – 500 |
| Copper | 100 – 200 | 300 – 600 |
| Cast iron (gray) | 50 – 80 | 200 – 400 |
| Mild / low-carbon steel (1018, A36) | 80 – 110 | 300 – 500 |
| Alloy / medium-carbon steel (1045, 4140) | 60 – 90 | 250 – 400 |
| Tool steel (hardened) | 40 – 60 | 150 – 300 |
| Stainless steel (304, 316) | 40 – 60 | 150 – 300 |
| Titanium alloy | 30 – 50 | 100 – 200 |
| Plastics (Delrin, acrylic, HDPE) | 400 – 800 | 600 – 1200 |
Recommended chip load (feed per tooth)
Chip load is the thickness each flute removes, in inches per tooth. Larger, more rigid tools take a bigger bite; small tools and tough alloys need a lighter one.
| End mill diameter | Aluminum / plastic | Mild steel | Stainless / titanium |
|---|---|---|---|
| 1/8 in (0.125) | 0.0010 – 0.0020 | 0.0005 – 0.0010 | 0.0004 – 0.0008 |
| 3/16 in (0.1875) | 0.0015 – 0.0025 | 0.0008 – 0.0015 | 0.0006 – 0.0010 |
| 1/4 in (0.250) | 0.0020 – 0.0040 | 0.0010 – 0.0020 | 0.0008 – 0.0015 |
| 3/8 in (0.375) | 0.0030 – 0.0050 | 0.0015 – 0.0030 | 0.0012 – 0.0020 |
| 1/2 in (0.500) | 0.0040 – 0.0060 | 0.0020 – 0.0040 | 0.0015 – 0.0030 |
| 3/4 in (0.750) | 0.0050 – 0.0080 | 0.0030 – 0.0050 | 0.0020 – 0.0035 |
| 1 in (1.000) | 0.0060 – 0.0100 | 0.0040 – 0.0060 | 0.0025 – 0.0040 |
These are conservative starting points for general milling. Always defer to your tooling manufacturer’s data, and adjust for rigidity, holder runout, coolant, depth of cut, and finish requirements.
How to use the chart
Example — a 1/2 in 4-flute carbide end mill in 6061 aluminum. Take 800 SFM: RPM = 800 × 3.82 / 0.5 = about 6,100 RPM. At 0.005 in chip load, feed = 6,100 × 0.005 × 4 = about 122 IPM. Drop the chip load and feed for slotting or deep cuts.
FAQ
What is SFM? Surface feet per minute — how fast the cutting edge travels past the material. It is set by the material and tool, independent of cutter size; RPM is what changes with diameter.
Why a chip load range instead of one number? The right value depends on rigidity, coolant, and whether you are roughing or finishing. The range brackets safe starting points; tune by sound, chip color, and finish.
How do I adapt this for a router or hobby CNC? Lighter machines flex more, so start at the low end of the chip load and reduce depth of cut. The SFM values still apply; you will just run a lower RPM ceiling on small spindles.
Related: Feeds & Speeds Calculators, Cutting & Tooling Calculators, and the Surface Finish Chart.