Tramming means mounting an indicator on an arm in the spindle and swinging it across the table, front to back and side to side, adjusting the head until readings match on opposite sides of the sweep. A knee mill with a tilting head needs it after any head move; an out-of-tram head leaves a dished or stepped surface when face milling or flycutting.
Somebody tilted the head for a chamfer and never trammed it back, look at the scallops on this flycut.
Sweep the biggest circle the table allows; the same tilt shows up as a bigger, easier-to-read difference.
Also heard as
- tram in
- tramming
Related terms
Sweep
To rotate an indicator in the spindle around a bore, boss or circle to find its center or check alignment.
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.
Bridgeport
Shop name for any vertical turret knee mill, after the brand that made the design standard.