M20×2.5 thread board

The part

Why so few rpm? The carriage moves 12 times faster than when turning and has to stop at Z-32.

Always X before Z: leave the way you came in.

G95: advance one pitch per rev. A thread is a helix.
G97: fixed rpm. If it changes, servo lag changes and passes don't land in the same groove.
Run-up distance before the part (here 12.5 mm = 5 pitches).

M20×2.5 external: root Ø16.93 (minor diameter)

Programmed: H2.86 → 1.43 mm per side

Nut: minor Ø = Ø17.294 > root Ø16.93: the nut goes on.

Check the first part with the M20×2.5 ring gauge.

n	Ø	depth	√n
1	18.887	0.452	1.00
2	18.512	0.639	1.41
3	18.225	0.783	1.73
4	17.982	0.905	2.00
…	…	…	…
10	16.931	1.430	3.16
11	16.931	1.430	—

Depth ∝ √n, so every pass removes the same chip section.

During threading Feed Hold doesn't work. Only Reset or emergency stop.

Stopping the carriage with the spindle running would wreck the thread. That's why everything must be checked beforehand.

Always check which control the program is for.

G71: 2 lines, the control works out the passes (+ spring pass).

G32: 55 lines, every pass by hand.

G32 is for learning what the cycle does inside. In production you use the cycle.

at the machine