Run-on

nounStandard termMachine Shop

The continued spinning of a machine spindle or tool after the power has been cut.

The freewheeling period where a heavy chuck, grinding wheel, or spindle keeps rotating due to inertia after the motor is turned off. It represents a safety hazard in older machines lacking electronic brakes, requiring the operator to wait for a complete stop before reaching in.

Heard on the job

Watch out for the run-on with that massive faceplate, it takes a good two minutes to stop spinning.

Also heard as

  • spindown