LinuxCNC G91.1

G91.1 is the LinuxCNC G-code that selects incremental arc distance mode for the I, J and K offsets used with G2 and G3 arc moves. In this mode the arc centre offsets are distances relative to the start location of the arc. G91.1 returns I, J and K to their default behaviour, which is incremental arc distance mode.

Source checked2/2 values · 2026-10-26

Specification

1 source

Language	gcode
Code	G91.1
Group	Arc Distance Mode
Dialect	LinuxCNC

Study notes

Incremental arc distance mode is the default mode for arc centre offsets.
In incremental arc distance mode, arc centre offsets are a relative distance from the start location of the arc.
The arc centre is treated as absolute or relative as set by G90.1 or G91.1 respectively.
In absolute arc distance mode (G90.1), both I and J must be given for arcs in the XY plane, or J and K for the XZ plane, otherwise it is an error.