No need to know the vocabulary first
A few words, explained
- Plunge
- A movement that takes a cutting tool down into material. Not every tool permits this.
- CNC
- Computer numerical control: a computer directs a cutting machine.
- Workholding
- The way you keep a piece securely in place while working on it.
- Feed rate
- How quickly a cutting tool moves along the material.
- RPM
- Revolutions per minute: how many full turns a tool makes each minute.
- Chip load
- The calculated forward distance per cutting edge; one way to understand how much each edge cuts.
2 more words used on this page
- Grain
- The direction and pattern of the wood's fibers.
- Flutes
- The grooves along a cutting bit; use the manufacturer's stated number of cutting edges in the calculation.
Choose the bit and operation first
An upcut, downcut, compression, straight, or ball-nose bit does not make the same cut. Define the material, flute count, diameter, and operation before choosing RPM, feed, or depth.
Check feed rate, RPM and flute count together
Feed rate, RPM, and flute count work together. Start from the tool manufacturer's guidance or a conservative calculation, then examine chips, heat, sound, and edge quality on matching scrap.
Record the full successful setup
Write down the wood species, bit, machine, RPM, feed, plunge, depth of cut, hold-down, and result. That record becomes a shop reference you can trust.
See it in an example
Understand the numbers before changing them
This is arithmetic practice only, not a recommended machine setting. Imagine a cutter moving 2,400 mm in one minute, spinning 16,000 times in that minute and having two cutting edges.
| Step | Example | What it means |
|---|---|---|
| Forward movement | 2,400 mm per minute | This is the feed rate. |
| Spinning speed | 16,000 turns per minute | This is the RPM. |
| Cutting edges | 2 | Check the bit manufacturer's information. |
| Distance per cutting edge | 2,400 ÷ (16,000 × 2) = 0.075 mm | This is the calculated chip load. |
Try it with your project
- Identify the material, exact bit, operation and machine limits.
- Use the bit manufacturer's guidance to choose an appropriate test plan. Keep the units consistent.
- Record the full setup and the result. Stop if the work is not secure or the cut behaves unexpectedly.
If forward movement stays the same and the spinning speed doubles, what happens to the calculated distance per edge?
It halves. More cutting edges pass the same distance in that minute. That explains why increasing spinning speed alone does not automatically improve a cut.
Further reading: ShopBot: feeds, speeds and chip-load calculation (opens a new tab)
Advanced practice
Compare CNC settings on matching stock
Start with tooling guidance, change one setting at a time and record how it affects the cut.
- Use a known bit and matching scrap material.
- Run a labeled test that changes only one variable at a time.
- Inspect edge quality, chips, heat, sound, and hold-down before choosing the next trial.
Try it with your own numbers
Common questions
What feeds and speeds should I use for wood CNC work?
Use the bit manufacturer's guidance and a calculator as the starting point, then make a controlled test on matching wood. Machine rigidity, bit geometry, hold-down, and desired finish all matter.
Why does CNC wood cutting burn or fuzz?
Heat, poor chip clearing, a dull bit, unsuitable feed or RPM, grain direction, and weak workholding can all affect the edge. Adjust one variable at a time during a test.
Should I save feeds and speeds by material?
Yes. Record the complete setup, including the bit and machine, so a proven result can be repeated rather than guessed again.