Spindle mode vs C-axis mode
| Mode | Behaviour | Post output |
|---|---|---|
| Spindle mode | Spindle rotates at speed for turning | M03/M04, S.. |
| C-axis indexing | Spindle positions and holds at an angle | C-axis on, C.., brake on |
| C-axis contouring | C moves with X/Z during milling | C-axis on, brake off, interpolation mode |
Switching modes safely
M05 (stop spindle)
M* (C-axis mode on - machine specific)
G28 H0. (reference C on many FANUC lathes)
G00 C0.
M* (C-axis brake on - machine specific)
(... cross drilling ...)
M* (brake off)
M* (C-axis mode off)C-axis engage, brake and reference methods vary between builders; we take them from the machine manual and proven programs.
Features machined with C-axis
- Face holes on a bolt circle (indexed C).
- Cross holes through the diameter (indexed C).
- Flats and hex forms on the face (polar interpolation).
- Slots and grooves on the diameter (cylindrical interpolation).
- Engraving and helical features.
Post details that matter
- C direction and zero relative to part features.
- Feed mode changes (
G98/G94per minute for milling vs per rev for turning). - Drilling cycles for face (
G83) and side (G87) on FANUC-type lathes. - Minimising C-axis unwinds between features.
The C-axis gives a lathe milling ability, and the post decides how smoothly it switches between the two.
C-axis lathe posts
See our CNC post processor development service and C-axis and live tooling output.