Setting correct cutting parameters is the difference between 30-minute tool life and 8-hour tool life. This guide gives you the formulas, a starting parameter chart, and worked examples.
Core Formulas
Spindle speed from cutting speed:
RPM = (Vc × 1000) / (π × D)
Where Vc is cutting speed in m/min and D is diameter in mm
Feed rate from chip load:
Fr = fz × N × RPM
Where fz is feed per tooth (mm), N is number of flutes
Material removal rate (MRR):
MRR = ae × ap × Fr (cm³/min, with dimensions in mm)
Starting Cutting Speeds (Vc) by Material
| Material | Carbide Vc (m/min) | HSS Vc (m/min) |
|---|---|---|
| Aluminum 6061 | 300–600 | 90–180 |
| Mild steel (1018) | 180–280 | 30–45 |
| Stainless 304 | 120–180 | 20–30 |
| Cast iron (gray) | 100–200 | 25–40 |
| Inconel 718 | 30–60 | 8–15 |
| Titanium Ti-6Al-4V | 60–90 | 15–25 |
Worked Example 1 — Turning
Turning a 50mm diameter shaft in 1045 steel with a CNMG carbide insert at Vc=220 m/min:
RPM = (220 × 1000) / (π × 50) = 1,401 RPM
Feed = 0.30 mm/rev × 1,401 = 420 mm/min
Worked Example 2 — Milling
Milling 6061 aluminum with a 12mm 3-flute carbide end mill at Vc=400 m/min, fz=0.12mm:
RPM = (400 × 1000) / (π × 12) = 10,610 RPM
Feed = 0.12 × 3 × 10,610 = 3,820 mm/min
Adjustment Factors
Multiply your starting parameters by these correction factors:
- Interrupted cut: 0.7×
- Roughing: 1.2× feed, 0.9× speed
- Finishing: 0.7× feed, 1.1× speed
- Worn tool: 0.85× speed
- Coolant on (vs dry): 1.1× speed
Practical Tip
Always start at 80% of recommended speed and increase 10% at a time while monitoring tool wear, chip color, and surface finish. Blue chips = too hot; reduce speed. Stringy chips = wrong chip breaker geometry.
Browse carbide inserts and end mills at Hooguu.
Shop Related Products at HOOGUU
