{"id":"gcode-g91-1","model_id":"G91.1","name":"LinuxCNC G91.1","summary":"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.","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."],"safety_notes":[],"sources":[{"url":"https://linuxcnc.org/docs/html/gcode/g-code.html#gcode:g90.1-g91.1","title":"G-Codes","accessed":"2026-10-26"}],"verification":{"status":"source_checked","checked_at":"2026-10-26","values":2,"method":"llm_source_check"},"updated_at":"2026-10-26","type":"instruction","spec":{"language":"gcode","code":"G91.1","group":"Arc Distance Mode","parameters":[],"dialect":"LinuxCNC","related":["gcode-g02"],"standards":[]},"url":"https://machineschema.com/instruction/gcode-g91-1","license":"https://creativecommons.org/licenses/by/4.0/"}