Calculators
End Mill Speeds & Feeds
Turn a cutting speed (SFM or m/min) and end-mill diameter into spindle RPM, and flute count + chip load (feed per tooth) into feed rate (in/min or mm/min) — with typical starting surface speeds and chip loads.
Last verified: 2026-07-09
Milling speed comes from the material's cutting speed and cutter diameter (RPM); feed rate is set by how many flutes are cutting and the chip load (feed per tooth). Enter your values below, then use the tables for starting cutting speeds and chip loads.
Units
Spindle speed
764 RPM
Feed rate
3.06 in/min
RPM = (cutting speed × K) ÷ (π × Ø); feed rate = RPM × flutes × chip load. Starting points only — always confirm against your tool manufacturer's data, material, machine rigidity, and coolant.
Typical starting cutting speeds
| Material | HSS (SFM) | Carbide (SFM) |
|---|---|---|
| Aluminum alloys | 250–400 | 600–1200+ |
| Brass | 150–250 | 400–700 |
| Mild steel (1018) | 70–100 | 300–500 |
| Alloy steel (4140) | 50–80 | 250–400 |
| Stainless (304) | 40–60 | 150–350 |
| Cast iron | 50–80 | 250–450 |
| Titanium | 30–50 | 100–250 |
Typical starting chip load (feed per tooth)
| Cutter Ø | Chip load (in/tooth) |
|---|---|
| 1/8" | 0.0005–0.0010 |
| 1/4" | 0.0010–0.0020 |
| 3/8" | 0.0015–0.0030 |
| 1/2" | 0.0020–0.0040 |
| 3/4"+ | 0.0030–0.0060 |
Frequently asked
- How is milling feed rate calculated?
- Feed rate = RPM × number of flutes × chip load (feed per tooth). RPM comes from the cutting speed and cutter diameter, exactly as in drilling. More flutes or a higher chip load means a faster feed for the same RPM.
- What chip load should I start with?
- It scales with cutter diameter — roughly 0.0005 in/tooth for a 1/8" up to 0.003–0.006 in/tooth for 3/4"+. Too light causes rubbing and work-hardening (especially in stainless); too heavy overloads the tool. Start mid-range and tune to the chips.
- Do I need to adjust for radial depth of cut?
- For light radial engagement (finishing, trochoidal), you can run higher chip loads or apply chip thinning; for full-width slotting, stay conservative. These figures are general starting points, not chip-thinned values.
Sources
- Standard machining speed/feed relationships (RPM from surface speed; feed = RPM × flutes × chip load)