The inaccuracy in a rotating system where the tool or workpiece does not spin perfectly true to its axis. It is measured with a dial indicator and caused by bent tools, dirty tapers, or worn bearings. Excessive runout causes uneven chip loads, chatter, and oversized holes.
Put an indicator on that endmill shank, I bet we've three thou of runout causing this chatter.
Total Indicator Reading (TIR) is the standard way to express runout, measuring the full sweep from the lowest to highest point on the dial.
Also heard as
- TIR
Related terms
Indicate
To align a vise, part or bore to the machine axes using a dial or test indicator.
Test indicator
A lever-type dial indicator with a swiveling stylus, used to align setups and compare surfaces.
Chatter
Self-sustaining vibration between tool and work that screams, leaves a wavy pattern and kills tools.