Siemens SINUMERIK 840D Function Manual page 137

The meaning is as follows:
F:
k :
e
k :
a
l :
G
The absolute value of F must be applied to G34 or G35 depending on the required pitch
increase of decrease.
When the thread length l
the end of block k
● For G34 (increasing pitch):
● For G35 (decreasing pitch):
Note
If the formula results in a negative root expression, the thread cannot be machined!
In this case, the NC signals alarm 10605 or alarm 22275.
Application
The G34 and G35 functions can be used to produce self-shearing threads.
Example
Thread cutting G33 with decreasing thread pitch G35
Program code
N1608 M3 S10
N1609 G0 G64 Z40 X216
N1610 G33 Z0 K100 SF=R14
N1611 G35 Z-220 K100 F17.045455
N1612 G33 Z-240 K50
N1613 G0 X218
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
The thread pitch change to be programmed [mm/rev
Thread pitch of axis target point coordinate, thread axis [mm/rev]
Initial thread pitch (programmed under I, J or K) [mm/rev]
Thread length [mm]
, pitch change F and initial pitch k
G
can be determined as follows by modifying the formula:
e
]
2
are known, the pitch increase at
a
Comment
; Spindle speed
; Approach starting point
; Thread with constant pitch 100 mm/rev
; Thread pitch decrease 17.045455 mm/rev2
; Thread pitch at end of block 50 mm/rev
; Traverse thread block without jerk
V1: Feedrates
5.2 Path feedrate F
137