Feed and Speed Calculator for Plywood: Chip Load Chart & RPM
Plywood's difficulty is structural, not thermal. Each ply runs at right angles to the one above it, so a cutter that produces a clean edge in one layer is cutting across the grain in the next.
For plywood, the recommended chip load runs from 0.127–0.203 mm per tooth on a 1/8″ cutter to 0.457–0.610 mm on a 1/2″. Typical spindle speeds sit between 16,000 and 18,000 RPM.
Your chip load is 0.3175 mm per tooth, which is within the recommended 0.254–0.381 mm range for plywood with a 6.35 mm upcut spiral.
Plywood. Alternating grain direction between plies means a compression bit earns its price here - it keeps both the top and bottom veneer intact.
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 plywood on a CNC router → - the full how-to: which bit, workholding, chip evacuation and reading the cut.
How plywood fails when the chip load is wrong
Tear-out on the top veneer, the bottom veneer, or both. An upcut bit lifts and splinters the top face; a downcut bit presses the top down cleanly but blows out the bottom as it exits. Neither geometry solves both faces on its own, which is the entire reason compression bits exist.
Setting up a cut in plywood
For visible plywood, a compression bit is the correct tool and the cost is justified in one sheet of birch ply. It needs a first pass deep enough to get the downcut portion into the material - a shallow first pass leaves you cutting with the upcut tip only, and you get exactly the tear-out you paid to avoid.
The thing most people get wrong
Voids. Cheaper plywood has internal gaps you cannot see, and the cutter's load changes abruptly when it hits one. If a machine is running near its limit, a void is where it will lose a step or snap a bit - leave more headroom on unknown material.
Chip-load reference for plywood
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) | 0.127 – 0.203 | 0.0050 – 0.0080 |
| 1/8" (3.18 mm) | 0.127 – 0.203 | 0.0050 – 0.0080 |
| 4 mm | 0.160 – 0.249 | 0.0063 – 0.0098 |
| 6 mm | 0.240 – 0.361 | 0.0094 – 0.0142 |
| 1/4" (6.35 mm) | 0.254 – 0.381 | 0.0100 – 0.0150 |
| 8 mm | 0.307 – 0.441 | 0.0121 – 0.0173 |
| 3/8" (9.53 mm) | 0.356 – 0.496 | 0.0140 – 0.0195 |
| 1/2" (12.70 mm) | 0.457 – 0.610 | 0.0180 – 0.0240 |
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.