Feeds & speeds calculator
Turn a target surface speed and chip load into a spindle RPM and feed rate for milling and routing, with material starting points and a copy-ready S/F G-code line.
Units
Starting points for carbide tooling, always verify against your cutter’s data.
Depth of cut & spindle limits
Spindle speed
13,263rpm
Feed rate
1,326 mm/min
Feed / rev
0.100 mm
Material removal
3.98 cm³/min
G-code
S13263 F1326spindle speed + feed, ready to paste into your program
Surface speed & chip load starting points
Typical carbide values for a ~6 mm cutter. Treat them as a starting point and tune from chip appearance, sound and finish, real numbers depend on your machine rigidity, tool and coolant.
| Material | Surface speed | Chip load |
|---|---|---|
| Aluminium | 250 m/min | 0.05 mm |
| Brass | 150 m/min | 0.05 mm |
| Mild steel | 90 m/min | 0.04 mm |
| Stainless steel | 55 m/min | 0.03 mm |
| Hardwood | 350 m/min | 0.12 mm |
| Softwood / MDF | 400 m/min | 0.15 mm |
| Acrylic (PMMA) | 300 m/min | 0.08 mm |
Frequently asked questions
How do I calculate spindle RPM?
Spindle RPM = (surface speed × 1000) ÷ (π × tool diameter) in metric, or (SFM × 12) ÷ (π × diameter) in inches. Choose the surface speed for your material and cutter, and this sets the spindle to the right cutting speed for that tool diameter.
What is chip load?
Chip load, or feed per tooth, is how much material each flute removes per revolution. Feed rate = RPM × number of flutes × chip load. Too low rubs and dulls the tool; too high overloads it and can break it.
Should I change speed or feed first?
Set RPM from a conservative surface speed, then raise the feed rate until the chips look right. Increasing feed generally helps tool life and finish more than chasing higher RPM.
Does it matter whether I use metric or imperial?
No. The calculator converts between m/min and mm and between SFM and inches, and both give the same spindle RPM. Use whichever units your machine and tooling data sheets use.
Why is the RPM higher than my spindle can reach?
Small cutters need very high RPM to hit a given surface speed. Use a larger diameter, lower the surface speed, or accept a lower cutting speed inside your spindle's range, the calculator warns you when the result exceeds your spindle maximum.
What chip load should I start with?
The material table lists carbide starting points for a roughly 6 mm cutter. Scale down for smaller or weaker tools and up for larger, rigid setups, then fine-tune from chip appearance, sound and finish.
rpm = (surface speed × 1000) ÷ (π × diameter); feed rate = rpm × flutes × chip load. Start conservative and increase feed before speed.