Chip Load Calculator
Chip load is the thickness of material each flute of an end mill removes per revolution. It is measured in inches per tooth (IPT) or millimeters per tooth. Programmed too low, the tool rubs instead of shearing and work-hardens the surface. Programmed too high, the tool deflects or fractures. This chip load calculator works in two modes: solve mode back-calculates the actual chip load from RPM, feed rate, and flutes; recommend mode pulls a baseline IPT for your material and tool diameter with optional chip-thinning correction.
The chip load formula
The chip load formula derives straight from the feed rate equation. For milling:
- Chip load (IPT) = Feed rate / (RPM x flutes)
- Equivalent form: Feed rate (IPM) = RPM x chip load x flutes
Example: a 4-flute end mill running 3,000 RPM at 24 IPM has chip load = 24 / (3000 x 4) = 0.002 IPT. That matches the standard 1/2 inch end mill baseline for mild steel.
Chip load chart by material
This is the baseline chip load chart for a 0.5 inch end mill. Smaller tools use less, larger use more.
| Material | Chip load (IPT) | Chip load chart mm (mm/tooth) |
|---|---|---|
| Aluminum 6061 | 0.004 | 0.102 |
| Mild steel (1018) | 0.002 | 0.051 |
| Alloy steel (4140) | 0.0015 | 0.038 |
| Stainless 304 | 0.0015 | 0.038 |
| Stainless 316 | 0.0012 | 0.030 |
| Tool steel | 0.001 | 0.025 |
| Cast iron | 0.003 | 0.076 |
| Brass | 0.003 | 0.076 |
| Titanium Ti-6Al-4V | 0.001 | 0.025 |
| Inconel 718 | 0.0008 | 0.020 |
| Plastic (Delrin) | 0.005 | 0.127 |
This chart serves as a chip load chart steel, chip load chart aluminum, and chip load calculator aluminum in one place. Values are baseline IPT for a 1/2 inch carbide end mill; multiply by 0.5-0.75 for 1/8-1/4 inch tools and by 1.25 for 3/4 inch and larger.
Chip thinning correction
When the radial width of cut is less than half the tool diameter, the actual chip the flute removes is thinner than the programmed IPT. The Sandvik chip-thinning correction scales chip load up by D / (2 x sqrt(Ae x (D - Ae))). At Ae = 10 percent of D, the factor is about 1.67x. A chip load calculator CNC setup that ignores this correction runs 40-60 percent lower than optimum whenever you take shallow radial cuts, wasting tool life to rubbing.
Imperial and metric
A chip load calculator metric user needs mm/tooth; a US shop uses IPT. The conversion is mm/tooth = IPT x 25.4. So 0.002 IPT equals 0.051 mm/tooth, and 0.004 IPT equals 0.102 mm/tooth. This calculator returns both.