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Machining & unit arithmetic

Cutting Speed & Spindle RPM Calculator

Convert an entered surface speed in metres per minute and effective cutting diameter in millimetres into rotational speed.

98 / CONVERT ENTERED CUTTING SPEED

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Starting values are illustrative. Use your own costs, rates and assumptions.

INPUT GROUP 01

Entered geometry and surface speed

Check the assumptions before acting on a result.

Read the method and example

YOUR CALCULATION

Translate an entered surface speed and effective diameter into rotational speed.

Calculated rotational speed (rpm)

1,909.859

Effective cutting circumference (m)

0.063

Calculated revolutions per second

31.831

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Illustrative inputs loaded. Replace them with your own assumptions.

How the cutting speed & spindle rpm calculator works

Effective circumference in metres is π times effective diameter in millimetres divided by 1,000. Revolutions per minute are surface metres per minute divided by that circumference. Equivalently, rpm = 1,000 × surface speed ÷ (π × diameter).

Diameter must be positive; zero surface speed gives zero rotation. Revolutions per second divide rpm by 60. Pi uses standard JavaScript numeric precision, and results describe the entered nominal quantities rather than a machine control instruction.

Effective cutting diameter may differ from cutter body diameter, particularly with shaped tools. No recommended speed, material parameter, engagement, machine limit, tool-life expectation, rigidity assessment or safe operating procedure is supplied. Verify actual process settings independently.

Worked example

At an entered 120 m/min surface speed and 20 mm effective diameter, circumference is about 0.062832 m and calculated spindle speed is about 1,909.859 rpm. At 150 m/min with the same diameter, the calculation gives about 2,387.324 rpm. Neither is a recommended setting.

Sources and assumptions

The source material explains the underlying calculation or pricing structure. Entered prices, costs, schedules and scenario choices are your assumptions; this tool does not obtain supplier quotes or predict actual results.

  • Milling Feed Rate & Travel Time

    Multiply entered RPM, effective teeth and chip load, then estimate ideal feed-travel time for a defined path and number of passes.

  • Machining Power & Torque

    Ideal cutting kW = removal rate in cm³/min × specific cutting force in N/mm² ÷ 60,000.

  • Milling Material Removal Rate

    Rectangular-engagement removal rate in cm³/min = axial millimetres × radial millimetres × table feed in mm/min ÷ 1,000.

  • Turning Material Removal Rate

    For the stated turning relation, material removal in cm³/min is surface speed in m/min × depth of cut in mm × feed in mm/revolution.

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