Feed rate is where speeds and feeds become a finish
Spindle RPM sets how fast the cutter turns; feed rate sets how fast it moves through the work. Get feed right and each tooth peels a proper chip that carries heat away. Too slow and the tool rubs and burns; too fast and it loads up and snaps. This calculator turns chip load and flute count into the table feed your machine actually wants.
The feed rate formula
Feed rate = RPM x feed per tooth x number of flutes. Feed per tooth (also called chip load) is how much each cutting edge advances per revolution. Multiply by the flute count to get feed per revolution, then by RPM to get distance per minute — inches per minute (IPM) or millimetres per minute.
Get your RPM first
Feed rate depends on spindle speed, so start with the RPM calculator to convert your material cutting speed and tool diameter into RPM, then bring that number here.
Typical chip loads
Rough starting chip loads for a half-inch carbide end mill. Smaller tools take lighter chips; scale down for tools under a quarter inch.
| Material | Chip load (in/tooth) |
|---|---|
| Aluminum | 0.004 – 0.006 |
| Brass / bronze | 0.002 – 0.004 |
| Mild steel | 0.002 – 0.003 |
| Stainless steel | 0.001 – 0.002 |
| Plastic | 0.004 – 0.006 |
Worked example
A 4-flute end mill at 3056 RPM with a 0.002 in chip load: feed = 3056 x 0.002 x 4 = 24.4 IPM, which is 0.008 in per revolution.
FAQ
Feed per tooth or feed per revolution?
Chip load is per tooth. A 4-flute cutter removes four chips per turn, so feed per revolution is four times the chip load. The calculator shows both.
What if my feed comes out too aggressive?
Reduce chip load, drop to a tool with fewer flutes, or lower RPM. Thin chips from a light load run cool but can cause rubbing if taken too far — aim for the middle of the range and adjust by sound and finish.