Feed and Speed Calculator for Hardwood: Chip Load Chart & RPM
Hardwood is the material that punishes a slow feed hardest. Oak, maple and walnut all conduct heat poorly, so the moment the cutter starts rubbing rather than shearing, the heat stays in the cut and scorches the surface.
For hardwood, the recommended chip load runs from 0.102–0.152 mm per tooth on a 1/8″ cutter to 0.381–0.533 mm on a 1/2″. Typical spindle speeds sit between 15,000 and 18,000 RPM.
Your chip load is 0.2795 mm per tooth, which is within the recommended 0.229–0.330 mm range for hardwood with a 6.35 mm upcut spiral.
Hardwood. Hardwood is the material where too slow a feed shows up fastest: the cutter rubs instead of cutting, heat builds, and the edge scorches. Burn marks mean feed up or RPM down, not the reverse.
Upcut spiral. The baseline the published charts assume. Chips are lifted clear of the cut, which keeps heat out of the workpiece at the cost of tear-out on the top surface.
How to cut hardwood on a CNC router → - the full how-to: which bit, workholding, chip evacuation and reading the cut.
How hardwood fails when the chip load is wrong
The signature failure is a burn mark, usually on the inside of a curve or wherever the machine slowed to change direction. Almost everybody's instinct on seeing a burn is to slow down further, which makes it worse. A burn means the chip is too thin to carry heat away: feed faster, or drop the spindle speed so the same feed produces a thicker chip.
Setting up a cut in hardwood
Grain direction matters more here than in any sheet good. Climb milling gives a cleaner surface on figured hardwood but loads the gantry harder and will pull a light machine into the work; conventional milling is safer on a hobby platform. Take the last pass as a light finishing cut with the same chip load rather than a slow spring pass.
The thing most people get wrong
Maple and cherry scorch at settings that oak tolerates perfectly. If you have dialled in a feed on oak, expect to raise it before moving to a lighter, denser hardwood - the density difference works against you and the pale surface shows every mark.
Chip-load reference for hardwood
Recommended chip load per tooth by cutter diameter, before any adjustment for depth of cut or bit geometry. Values between the 1/8″, 1/4″ and 1/2″ anchors are interpolated.
| Cutter diameter | Chip load (mm/tooth) | Chip load (in/tooth) |
|---|---|---|
| 1/16" (1.59 mm) | 0.102 – 0.152 | 0.0040 – 0.0060 |
| 1/8" (3.18 mm) | 0.102 – 0.152 | 0.0040 – 0.0060 |
| 4 mm | 0.135 – 0.198 | 0.0053 – 0.0078 |
| 6 mm | 0.215 – 0.310 | 0.0085 – 0.0122 |
| 1/4" (6.35 mm) | 0.229 – 0.330 | 0.0090 – 0.0130 |
| 8 mm | 0.268 – 0.383 | 0.0106 – 0.0151 |
| 3/8" (9.53 mm) | 0.305 – 0.432 | 0.0120 – 0.0170 |
| 1/2" (12.70 mm) | 0.381 – 0.533 | 0.0150 – 0.0210 |
These are estimates derived from published tooling-manufacturer data, not test results. Always prove a new setting on scrap first. Sources are listed on the methodology page.
Other materials
Already running a feed rate and want to know what chip load it produces? Use the chip load calculator.