CNCJune 25, 2026· JP T
A sane starting point for feeds and speeds
Chip load is the number that matters. Start here, listen to the cut, and adjust.
New CNC operators chase RPM. Experienced ones chase chip load — how much material each flute takes per revolution. Get that right and the rest falls out of the math.
The one equation
Feed rate = RPM × number of flutes × chip load. That's it. Pick a conservative chip load for your material, set a safe RPM for your bit diameter, and let the feed follow.
- Soft woods: start around 0.05–0.10mm/tooth.
- Hardwoods and plywood: 0.03–0.08mm/tooth.
- Aluminium: 0.02–0.05mm/tooth, and use lubricant.
Then listen
A good cut sounds steady, throws chips (not dust), and leaves a clean wall. Dust means you're rubbing — push the feed up. Screaming means you're too aggressive — back it off.
The Feed & Speed tool bakes these defaults in so you never start from a blank field.
Frequently asked questions
- What is chip load in CNC machining?
- Chip load is how much material each flute removes per revolution. It's the number experienced operators chase instead of RPM — get it right and the feed rate falls out of the math.
- What is the formula for CNC feed rate?
- Feed rate = RPM × number of flutes × chip load. Pick a conservative chip load for your material, set a safe RPM for your bit diameter, and let the feed follow.
- What chip load should I start with?
- Rough starting points: soft woods 0.05 to 0.10mm per tooth, hardwoods and plywood 0.03 to 0.08, aluminium 0.02 to 0.05 with lubricant. Start conservative and adjust.
- How do I know if my feeds and speeds are right?
- Listen to the cut. A good one sounds steady, throws chips instead of dust, and leaves a clean wall. Dust means you're rubbing — push the feed up. Screaming means you're too aggressive — back it off.