Machining Surface Speed Calculator

Calculate the linear speed at a rotating tool or workpiece circumference from spindle RPM and diameter, or solve the formula backward for RPM. Unlike a rotational-speed conversion, surface speed depends on both rotation rate and diameter. Calculate it clearly with Figur.

How the machining surface speed calculator works

Calculate the linear speed at a rotating tool or workpiece circumference from spindle RPM and diameter, or solve the formula backward for RPM. Unlike a rotational-speed conversion, surface speed depends on both rotation rate and diameter.

Method and assumptions

Figur uses surface speed = π × diameter × RPM. It converts diameter to meters, calculates circumference speed in m/min, and converts to SFM when requested. To solve for RPM, it divides surface speed by π × diameter.

  • The entered diameter is the effective cutting diameter of the tool or workpiece.
  • RPM and diameter remain constant for the calculation.
  • SFM means linear feet per minute at the circumference; m/min represents the same quantity in metric units.

This calculator relates RPM, diameter, and surface speed. It does not recommend cutting speeds, feeds, chip load, tooling limits, or safe machine settings.

Sources and references

Worked example

Find the surface speed of a 2-inch diameter tool at 1,000 RPM.

The surface speed is 523.598775598 SFM, or approximately 159.592906802 m/min.

Frequently asked questions

How is machining surface speed calculated?

Surface speed equals π × diameter × RPM, with diameter converted to feet for SFM or meters for m/min.

Is surface speed the same as rotational speed?

No. RPM describes revolutions per minute. Surface speed describes linear distance traveled at the circumference, so the same RPM produces a higher surface speed at a larger diameter.

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