CNC Machining worked example

CNC Feed Rate with spindle speed of 4,000 RPM: a worked example

Suppose spindle speed falls to 4,000 RPM. This page works the full calculation at that level so you can see exactly which result moves and by how much. Calculate CNC feed rate from spindle speed, flute count, chip load, and feed override for milling, routing, drilling, or similar rotating-tool operations.

The inputs for this scenario

  • Spindle speed: 4,000 RPM (the input this scenario stresses; the baseline uses 8,000)
  • Flutes or teeth: 3 count (held at the documented default)
  • Chip load: 0 in / tooth (held at the documented default)
  • Feed override: 1 x (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Feed rate = spindle speed × flutes or cutting teeth × chip load per tooth × feed override.
  • programmed CNC feed rate works out to 48 in / min at these inputs, and this is the headline figure for the scenario.
  • Base product works out to 48 value at these inputs.
  • Multiplier works out to 1 x at these inputs.
  • Factor A x B works out to 12,000 value at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where spindle speed sits at 8,000 RPM and the headline result is 96 in / min, this scenario comes in 50% below the baseline at 48 in / min.
  • It computes the programmed feed rate in inches per minute by multiplying spindle speed, flute count, chip load per tooth, and any feed override. When the numbers land here, the stressed input is the lever to work; the walkthrough above shows exactly how much each output recovers as it climbs back toward the baseline.

Results at a glance

  • programmed CNC feed rate: 48 in / min (headline result)
  • Base product: 48 value
  • Multiplier: 1 x
  • Factor A x B: 12,000 value

Run it with your numbers

  • To rerun this with your own numbers, open the live CNC Feed Rate calculator, set spindle speed to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.