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Machining Cutting Speed Calculator

Calculate Surface Speed (Vc) or Spindle Speed (RPM) for Milling, Turning, and Drilling.

Unit System Metric (mm, m/min) Imperial (inch, SFM)

Tool/Workpiece Diameter mm

Spindle Speed (RPM)

Number of Teeth/Flutes (Optional)

Feed per Tooth (Optional) mm/tooth

Cutting Speed (Vc): 0

Table Feed Rate (Vf): 0

Understanding Cutting Speed in Machining

Cutting speed, often denoted as Vc (Velocity of Cutting) or SFM (Surface Feet per Minute), refers to the speed at which the cutting edge of the tool moves relative to the workpiece. It is a critical parameter in CNC machining, manual milling, and lathe work because it directly impacts tool life, surface finish, and heat generation.

The Mathematics of Cutting Speed

The formula for cutting speed depends on whether you are using the Metric system or the Imperial system:

Metric (m/min): Vc = (π × D × n) / 1000
Imperial (SFM): SFM = (π × D × n) / 12

Where:

D: Diameter of the tool (milling) or workpiece (lathe).
n: Spindle speed in Revolutions Per Minute (RPM).
π (Pi): Approximately 3.14159.

Typical Cutting Speeds by Material

Choosing the right cutting speed is essential. Using a speed that is too high will cause rapid tool wear (cratering or plastic deformation), while a speed that is too low results in poor efficiency and potential built-up edge (BUE).

Material	Metric (m/min)	Imperial (SFM)
Aluminum (6061)	250 – 500	800 – 1600
Low Carbon Steel	100 – 150	320 – 500
Stainless Steel (304)	50 – 90	160 – 300
Titanium Alloys	40 – 60	130 – 200
Cast Iron	80 – 120	260 – 400

Why Feed Rate Matters

While cutting speed dictates the heat, the Feed Rate (Vf) dictates the chip load. Our calculator also provides the Table Feed Rate if you provide the number of flutes and the feed per tooth. The formula is:

Vf = n × fz × z

Where fz is the feed per tooth and z is the number of flutes. Balancing Vc and Vf ensures the highest material removal rate (MRR) without breaking the tool.

Example Calculation

If you are milling with a 12mm Carbide End Mill at 3000 RPM in the Metric system:

Vc = (3.14159 × 12 × 3000) / 1000 = 113.1 m/min.

If you have 4 flutes and a feed per tooth of 0.08mm, your table feed would be: 3000 × 0.08 × 4 = 960 mm/min.