Coolant control (M08, M09) in CNC Programming

Introduction

Coolant helps keep tools and workpieces cool during machining. M08 turns coolant on, and M09 turns it off.

When starting a cutting operation to cool the tool and workpiece.

When finishing a cut and you want to stop the coolant flow.

To prevent overheating and improve tool life during drilling or milling.

When switching between different machining steps that require coolant on or off.

To keep the work area clean by controlling coolant spray.

Syntax

CNC Programming

M08 ; Turn coolant ON
M09 ; Turn coolant OFF

M08 activates the coolant system.

M09 stops the coolant flow.

Examples

This command turns the coolant on before starting a cut.

CNC Programming

M08

This command turns the coolant off after finishing a cut.

CNC Programming

M09

Starts cutting with coolant on, then moves to a new position, and finally turns coolant off.

CNC Programming

G01 X50 Y50 F100 M08
G01 X100 Y100 F100
M09

Sample Program

This program turns coolant on before cutting moves and turns it off at the end.

CNC Programming

O1000 (Sample program for coolant control)
G21 (Set units to mm)
G90 (Absolute positioning)
M08 (Turn coolant ON)
G01 X50 Y50 F200 (Cutting move)
G01 X100 Y100 F200 (Cutting move)
M09 (Turn coolant OFF)
M30 (End program)

Important Notes

Always turn coolant off (M09) at the end to avoid wasting coolant.

Some machines may have different coolant commands; check your machine manual.

Coolant helps reduce tool wear and improves surface finish.

Summary

M08 turns coolant on to cool tools and workpieces.

M09 turns coolant off to stop coolant flow.

Use these commands to protect tools and improve machining quality.