Cutting Parameter Calculator
Once the material group, cutting diameter and flute count are entered, the spindle speed (n), feed per tooth (fz), table feed (vf), metal removal rate (Q) and the required spindle power are calculated. Where the radial engagement is smaller than half the diameter, the chip thinning correction is applied automatically.
Inputs
Example: 42CrMo4, 1.7225, 4140
Suggested: 4
Default 12,000. Change it for your machine; leave empty to see the theoretical value.
80 – 150
0.016 – 0.030
Frequently asked questions
How is spindle speed calculated in milling?
Short answer: n = (Vc × 1000) / (π × D). Vc is the cutting speed (m/min) and D the cutting diameter of the tool (mm). For Vc = 120 m/min and D = 8 mm this gives n = (120 × 1000) / (3.1416 × 8) ≈ 4,775 rpm.
How is the table feed (vf) found?
Short answer: vf = fz × z × n. fz is the feed per tooth (mm/tooth), z the number of flutes and n the spindle speed. fz is taken from a table by material group and diameter; where the radial engagement ae is smaller than half the diameter, it is multiplied by the chip thinning correction.
What is chip thinning and why does it matter?
When the radial engagement ae drops below D/2, the actual chip thickness becomes smaller than fz. Without the correction the tool rubs instead of cutting: heat rises, the edge wears quickly and the surface degrades. The correction factor is RCTF = 1 / (2 × √((ae/D) × (1 − ae/D))) and fz is multiplied by it.
What determines the cutting speed Vc?
Vc depends on the ISO group of the workpiece material (P steel, M stainless, K cast iron, N non-ferrous, S superalloys, H hardened steel), on the tool substrate and on the coating. This calculator assumes a carbide tool with a suitable coating and uses group-based ranges; the duty slider sets where within the range the work is carried out.
Can the calculated values be entered directly at the machine?
The values are starting values. Machine rigidity, holder runout, workholding and the coolant method change the outcome. Holding the spindle speed on the first trial, raising the feed step by step and watching the chip colour and the cutting sound is regarded as the safest method.
Formulas used
| Quantity | Formula | Unit |
|---|---|---|
| Spindle speed | n = (Vc × 1000) / (π × D) | rpm |
| Cutting speed | Vc = (π × D × n) / 1000 | m/min |
| Table feed | vf = fz × z × n | mm/min |
| Feed per tooth | fz = vf / (z × n) | mm/tooth |
| Chip thinning correction | RCTF = 1 / (2 × √((ae/D) × (1 − ae/D))) | – |
| Average chip thickness | hex = fz × 2 × √((ae/D) × (1 − ae/D)) | mm |
| Metal removal rate | Q = (ap × ae × vf) / 1000 | cm³/min |
| Spindle power | P = (ap × ae × vf × kc) / (60 × 10⁶ × η) | kW |
D cutting diameter (mm) · z number of flutes · ap axial depth of cut (mm) · ae radial width of cut (mm) · kc specific cutting force (N/mm²) · η machine efficiency (≈ 0.80).