M07 is the M-code that turns on mist coolant. It’s a modal command, meaning it stays on until you cancel it. Mist coolant mixes coolant fluid with compressed air and sprays the cutting area instead of flooding it.
Key Takeaways
- M07 turns on mist coolant — a mix of coolant fluid and compressed air
- It’s a modal command: stays on until cancelled with M09 or a program stop
- Less common than flood coolant (M08), but useful for specific materials and setups
- Not all CNC machines support M07 — always check your machine’s documentation
- Cancel mist coolant with M09, or it turns off automatically on M00, M01, M02, and M30
| M07 – At A Glance | |
|---|---|
| Function | Mist Coolant On |
| Type | Modal |
| Cancelled by | M09, M00, M01, M02, M30 |
| Machine support | Not universal — check your control |
What Does M07 Do?
When the CNC control reads M07, it activates the mist coolant system. The machine combines coolant fluid with compressed air and sprays it directly at the cutter and workpiece.
Mist coolant does three things: it lubricates the cutter, helps clear chips away from the cut zone, and reduces heat buildup. It uses less coolant fluid than flood coolant and tends to be less messy depending on your machine setup.
M07 Mist Coolant vs. M08 Flood Coolant
Flood coolant (M08) is what you’ll see on most CNC machining centers. It dumps a heavy flow of coolant fluid directly over the cutter and part. That works well for most metals — it keeps temperatures down and flushes chips out of the way.
Mist coolant (M07) uses a fraction of that fluid. It’s better suited for materials that are sensitive to large amounts of coolant, like some aluminum alloys, composites, or certain cast irons. It’s also used when your machine’s coolant system isn’t set up for high-volume flood.
The tradeoff: mist coolant isn’t as effective at pulling heat out of the cut. For heavy material removal rates or tough materials like stainless steel, flood coolant is almost always the better choice.
M07 in a CNC Program
Here’s a simple example of M07 used in a milling program. The coolant comes on before the cut and gets cancelled at the end.
G90 G54 G00 X0. Y0. (Absolute mode, work offset, rapid to start)
G43 H01 Z1.0 M07 (Tool length comp, mist coolant ON)
G01 Z-0.250 F10.0 (Feed into cut)
X4.0 (Contour move)
G00 Z1.0 (Rapid retract)
M09 (Coolant OFF)
G91 G28 Z0. (Return Z to home)
M30 (Program end)M07 is called on the same line as the first tool move into position. M09 cancels the coolant before the tool retracts home. This is a common pattern — you want coolant on during the cut, off before the program ends.
Other Coolant Options on CNC Machines
Besides mist (M07) and flood (M08), some machines offer additional coolant delivery methods:
Air blast — Compressed air only, no fluid. It clears chips and reduces heat, but provides no lubrication. Often used for dry machining of certain plastics or composites where coolant would cause problems.
High-pressure coolant — Similar to flood coolant but delivered at over 1,000 psi. The high pressure improves chip evacuation significantly, especially in deep holes or pockets. Requires a machine equipped with a high-pressure pump.
Through-spindle coolant — Coolant is delivered through the center of the spindle and out through the cutting tool itself. This puts coolant exactly where it’s needed and is highly effective for drilling deep holes. Requires specially designed tooling with internal coolant passages.
How to Turn Off Mist Coolant
Use M09 to cancel mist coolant. It cancels all coolant — mist, flood, or any other active coolant mode.
M09 (Cancel all coolant)Several other program stop commands also cancel coolant automatically as part of their function:
- M00 — Program stop (machine pauses, operator must restart)
- M01 — Optional stop (pauses only if the optional stop switch is active on the control)
- M02 — Program end, no rewind
- M30 — Program end with rewind to top of program
In most shops, you’ll see M09 programmed explicitly before any tool change or program end. It’s good practice — don’t rely on M30 to handle it for you.
Frequently Asked Questions About the M07 Code
Does every CNC machine support M07?
No. Many machining centers only support M08 for flood coolant. M07 is less commonly implemented, especially on older equipment. Before using M07 in a program, check your machine’s M-code list in the programming manual or control documentation.
Can you run M07 and M08 at the same time?
No. Only one coolant mode should be active at a time. If you program M08 while M07 is active, the control will typically switch to flood coolant. Always cancel coolant with M09 before switching modes.
What cancels M07?
M09 cancels mist coolant. M00, M01, M02, and M30 also cancel it as part of their stop functions.
When would you choose M07 over M08?
When you’re machining a material that’s sensitive to high-volume coolant, when your machine’s coolant tank is low and you need to conserve fluid, or when your setup requires a cleaner work environment with less coolant splatter. That said, M08 is the default choice for most metal cutting operations.