{"id":"mcode-m08","model_id":"M8","name":"LinuxCNC M8","summary":"M8 is a LinuxCNC M-code that turns flood coolant on. It does so by controlling the iocontrol.0.coolant-flood HAL pin, which must be connected in HAL before the command affects a physical output. M9 turns both mist (M7) and flood (M8) coolant off.","study_notes":["M8 controls the iocontrol.0.coolant-flood pin.","M7 controls the iocontrol.0.coolant-mist pin.","M9 turns both M7 and M8 off.","One or both coolant control pins must be connected in HAL before M7 or M8 will control an output; M7 and M8 can be used to turn on any output via G-code.","It is OK to use M7, M8 or M9 regardless of the current coolant state.","M2/M30 program end turns coolant off like M9.","M70 saves mist (M7) and flood (M8) status as part of modal state."],"safety_notes":[],"sources":[{"url":"https://linuxcnc.org/docs/html/gcode/m-code.html#mcode:m7-m8-m9","title":"M-Codes","accessed":"2026-10-26"}],"verification":{"status":"source_checked","checked_at":"2026-10-26","values":3,"method":"llm_source_check"},"updated_at":"2026-10-26","type":"instruction","spec":{"language":"gcode","code":"M8","group":"Coolant Control","syntax":"M8","parameters":[],"dialect":"LinuxCNC","related":[],"standards":[]},"url":"https://machineschema.com/instruction/mcode-m08","license":"https://creativecommons.org/licenses/by/4.0/"}