CNC Chip Load Chart
Chip load, also written chipload, is the one number that decides whether your bit cuts clean or burns, chatters, and snaps. Below are safe starting values (feed per tooth, in inches) for common hobby materials and bit sizes. Find your material and bit, then feed the number into the formula, or skip the math and let our feeds and speeds calculator do it for you.
The only formula you need
Feed rate = chipload × number of flutes × RPM
Example: a 0.003" chipload on a 2-flute bit at 18,000 RPM = 0.003 × 2 × 18,000 = 108 IPM.
Chip Load by Material & Bit Diameter
Values are inches per tooth (feed per tooth). Bold = target; the range underneath is the safe window.
| Material | 1/8" bit | 1/4" bit | 3/8" bit | 1/2" bit |
|---|---|---|---|---|
| Softwood Pine, cedar, poplar | 0.002" 0.001-0.003 | 0.003" 0.002-0.005 | 0.004" 0.003-0.006 | 0.005" 0.004-0.007 |
| Hardwood Oak, maple, walnut | 0.0015" 0.001-0.002 | 0.0025" 0.001-0.004 | 0.003" 0.002-0.005 | 0.004" 0.003-0.006 |
| Plywood / MDF Baltic birch, MDF | 0.002" 0.001-0.003 | 0.003" 0.002-0.005 | 0.004" 0.003-0.006 | 0.005" 0.004-0.007 |
| Acrylic Cast & extruded | 0.002" 0.001-0.003 | 0.004" 0.003-0.006 | 0.005" 0.004-0.007 | 0.006" 0.005-0.008 |
| HDPE / Plastics HDPE, Delrin, nylon | 0.003" 0.002-0.004 | 0.005" 0.004-0.008 | 0.006" 0.004-0.008 | 0.007" 0.005-0.01 |
| Aluminum 6061, needs lubricant | 0.001" 0.0005-0.002 | 0.002" 0.001-0.003 | 0.0015" 0.001-0.003 | 0.002" 0.001-0.003 |
Starting points for hobby CNC routers, gathered from manufacturer charts and community consensus. Always start at the low end, listen to the cut, and dial up. Aluminum needs lubricant and much shallower passes.
How to Use This Chart
- Find your material row and your bit diameter column. The bold number is your target chipload.
- Count the flutes on your bit (most beginner bits are 2-flute).
- Pick your RPM (router dial setting). Lower RPM + same feed = bigger chips.
- Multiply: chipload × flutes × RPM = feed rate in inches per minute.
- Cut a test piece, check the chips and sound, and adjust. Dust means you're too slow; clean chips means you're dialed in.
Don't Want to Do the Math?
Our free calculator has this chart built in. Pick your machine, bit, and material, and it gives you safe RPM, feed rate, and depth of cut instantly, and remembers your setup for next time.
Open the Feeds & Speeds Calculator →Bits Worth Owning
The chart assumes decent carbide bits. If you're still running the freebies that came with your machine, these are the community favorites we'd start with:
- →1/4" 2-flute upcut spiral, the workhorse for clearing wood fast.
- →1/8" 2-flute downcut, clean top edges on detailed work.
- →Single-flute O-flute, the one that finally makes acrylic behave.
Some links are affiliate links. We only point to bits the community actually recommends. How this works.
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Chipload FAQ
What is chip load (chipload) on a CNC?
Chip load, also written chipload, is how far the cutter advances per flute per revolution, measured in inches. It sets the chip thickness. Too low and the bit rubs and overheats; too high and it chatters or snaps. Feed rate = chip load x number of flutes x RPM.
How do I turn chipload into a feed rate?
Multiply chipload by the number of flutes and the spindle RPM. Example: a 0.003" chipload on a 2-flute bit at 18,000 RPM = 0.003 x 2 x 18,000 = 108 inches per minute.
What chipload should a beginner start with?
For a 1/4" 2-flute bit in softwood or plywood, start around 0.003" per tooth and adjust by sound and chips. Go lower for hardwood and much lower for aluminum. Always start conservative and dial up.