Feed and Speed Calculator for Acrylic: Chip Load Chart & RPM
Acrylic fails by melting rather than burning, which inverts the intuition that works for wood. The chip is not a by-product here - it is the cooling system, and it has to leave the cut carrying heat with it.
For acrylic, the recommended chip load runs from 0.102–0.152 mm per tooth on a 1/8″ cutter to 0.330–0.483 mm on a 1/2″. Typical spindle speeds sit between 12,000 and 16,000 RPM.
Your chip load is 0.2540 mm per tooth, which is within the recommended 0.203–0.305 mm range for acrylic with a 6.35 mm upcut spiral.
Acrylic. Acrylic fails by melting, not by burning. The chip has to carry the heat away, so an under-fed cut welds the swarf back onto the cutter. Single-flute O-flute geometry is the standard answer.
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 acrylic on a CNC router → - the full how-to: which bit, workholding, chip evacuation and reading the cut.
How acrylic fails when the chip load is wrong
Melted, re-welded swarf gumming the flutes, and a cut edge that is cloudy or has a bead of resolidified plastic along it. That happens when the chip is too thin: it lacks the mass to absorb the heat, so the heat goes into the workpiece and the plastic softens instead of shearing.
Setting up a cut in acrylic
Single-flute O-flute geometry is the standard answer, because one large chip per revolution carries away far more heat than two small ones. Lower spindle speeds than you would use for wood, combined with a healthy feed, are what keep the chip thick.
The thing most people get wrong
Cast and extruded acrylic behave differently. Cast machines cleanly; extruded is softer, gummier and far more prone to melting at the same settings. If a sheet that used to cut perfectly suddenly gums up, check which type you bought before you change the feed.
Chip-load reference for acrylic
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 | 0.128 – 0.192 | 0.0050 – 0.0075 |
| 6 mm | 0.192 – 0.288 | 0.0076 – 0.0113 |
| 1/4" (6.35 mm) | 0.203 – 0.305 | 0.0080 – 0.0120 |
| 8 mm | 0.236 – 0.351 | 0.0093 – 0.0138 |
| 3/8" (9.53 mm) | 0.267 – 0.394 | 0.0105 – 0.0155 |
| 1/2" (12.70 mm) | 0.330 – 0.483 | 0.0130 – 0.0190 |
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.