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Cutting Speed and Feed Calculator

Spindle speed, feed rate, metal removal rate and power for turning, milling and drilling.

Get spindle RPM, table feed and metal removal rate for turning, milling and drilling from cutting speed and diameter. Recommended starting speeds are built in for carbide and HSS tools across carbon steel, alloy steel, stainless steel, cast iron, aluminium and brass.

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  • Full step-by-step working
  • PASS / FAIL checks
  • Free PDF report

Inputs

Results

Spindle speed
1082 rpm
Feed rate
216.5 mm/min
Removal rate
68 cm³/min
Motor power
2.975 kW
Step-by-step calculation (6 steps)
  1. 1Cutting speed
    FormulaVc = Vc,ref × operation factor
    SolutionVc = 170 × 1 [Medium carbon steel C45 / EN8, carbide, turning]
    ResultVc = 170 m/min
  2. 2Spindle speed
    Formulan = 1000·Vc / (π·D)
    Solutionn = 1000 × 170 / (π × 50)
    Resultn = 1082 rpm
  3. 3Feed rate
    FormulaVf = f·n
    SolutionVf = 0.2 × 1082
    ResultVf = 216.5 mm/min
  4. 4Metal removal rate
    FormulaQ = Vc·f·ap [cm³/min]
    SolutionQ = 170 × 0.2 × 2
    ResultQ = 68 cm³/min
  5. 5Cutting power
    FormulaPc = Q·kc / 60 000
    SolutionPc = 68 × 2100 / 60 000 [kc = 2100 N/mm²]
    ResultPc = 2.38 kW
  6. 6Spindle motor power
    FormulaPm = Pc / η
    SolutionPm = 2.38 / 0.8
    ResultPm = 2.975 kW

Engineering takeaways

  • Recommended speeds are conservative starting values. Use the tool supplier's data for the exact grade and coating.
  • If chatter appears, reduce depth of cut before reducing speed. Speed mainly affects tool life; feed and depth drive power.
  • Specific cutting force kc rises at small chip thickness, so light finishing cuts use more power per cm³ than shown.

The PDF report contains every input, formula, substitution and check shown above, in LTM calculation-sheet format.

Worked Example

The calculator also estimates cutting power from specific cutting force, and spindle motor power after machine losses, so you can check whether a machine can take the cut.

The calculator above opens with this example. Change any input to run your own case.

Inputs

OperationTurning
Workpiece materialMedium carbon steel C45 / EN8
Tool materialCoated carbide
Cutting speed sourceUse recommended starting value
Diameter D (work for turning, tool for milling/drilling)50 mm
Feed per revolution f0.2 mm/rev
Depth of cut ap2 mm
Machine efficiency η0.8
Spindle max speed (0 = no limit)0 rpm

Results

Spindle speed1082 rpm
Feed rate216.5 mm/min
Removal rate68 cm³/min
Motor power2.975 kW

Cutting Speed Formulas Used

Spindle speed

n=1000 Vcπ Dn = \frac{1000\,V_c}{\pi\,D}
  • Vccutting speed (m/min)
  • Dworkpiece or tool diameter (mm)

Feed rate

Vf=f⋅n  (turning, drilling),Vf=fz z n  (milling)V_f = f\cdot n\ \ (\text{turning, drilling}),\qquad V_f = f_z\,z\,n\ \ (\text{milling})
  • fzfeed per tooth
  • znumber of teeth

Metal removal rate

Qturn=Vc f ap,Qmill=ap ae Vf1000,Qdrill=πD24⋅Vf1000Q_{turn} = V_c\,f\,a_p,\qquad Q_{mill} = \frac{a_p\,a_e\,V_f}{1000},\qquad Q_{drill} = \frac{\pi D^2}{4}\cdot\frac{V_f}{1000}
  • Qin cm³/min

Cutting power

Pc=Q⋅kc60 000 kW,Pm=PcηP_c = \frac{Q\cdot k_c}{60\,000}\ \text{kW},\qquad P_m = \frac{P_c}{\eta}
  • kcspecific cutting force (N/mm²)
  • ηmachine efficiency

Basis: Standard machining relationships; typical kc values for workpiece groups. Results are for preliminary design and should be confirmed against supplier data and the governing standard.

Cutting Speed Calculator FAQ

How do I calculate spindle RPM from cutting speed?

Divide 1000 × Vc by π × D. For 170 m/min on a 50 mm bar: 1000 × 170 / (π × 50) ≈ 1082 rpm.

What cutting speed should I use for mild steel?

Coated carbide inserts typically run 180 to 250 m/min in low carbon steel; HSS tools about 25 to 35 m/min. The calculator uses 200 and 30 m/min as starting points. Fine-tune from tool wear and surface finish.

Why does drilling use a lower cutting speed?

Chip evacuation and heat at the drill point are harder to manage, and the centre of the drill cuts at almost zero speed. The calculator applies 60% of the turning speed as a safe starting value.

What is specific cutting force kc?

kc is the force needed to remove a chip of 1 mm² cross-section. It is about 2000 N/mm² for carbon steel, 2400 for stainless and 700 for aluminium, and it rises as the chip gets thinner.

How do I increase metal removal rate?

Increase depth of cut and feed first; they raise removal rate with little effect on tool life. Raising cutting speed shortens tool life quickly. Check that spindle power and rigidity can take the heavier cut.

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