A complete tool change sequence
(End of previous tool)
M09 (coolant off)
M05 (spindle stop - if required by machine)
G91 G28 Z0. (safe Z)
G90
(Tool change)
T7 M06
(TOOL 7 - D10 CARBIDE DRILL)
T8 (pre-select next tool)
(Start of new tool - restart point)
G90 G54 G00 X25. Y15. S3200 M03
G43 H07 Z50. M08Decisions the post makes
| Decision | Options |
|---|---|
| Where to change | Machine home Z, specific XYZ, or builder macro handles it |
| Spindle stop before M06 | Explicit M05 or automatic |
| Pre-select | Output next T after M06 if supported |
| Same tool, next operation | Skip tool change, keep spindle on |
| Tool break check | Call a probe or laser check after critical tools |
| Rotary position | Return rotaries to safe angle before change (5-axis) |
Restart-safe tool blocks
Every tool block should contain everything needed to start from there: work offset, absolute mode, spindle speed and direction, coolant and length offset. Operators can then restart safely from any tool after a breakage or inspection.
Lathe turret tool changes
On lathes, T0303 indexes the turret and applies offset 3. The post moves to a safe index position first, so the turret doesn't hit the chuck, tailstock or part when it rotates.
A well-designed tool change is a safe restart point, every time.
Tool change customisation
See our CNC post processor development service and safe retract strategies.