On 10/19/26 07:23, andy pugh wrote:
I wonder where it got this idea from? (in Master one can use "D" for
this, H remains spring passes)
------begin AI slop-------
LinuxCNC G-Code Approach (G76)
In LinuxCNC, multi-start threading is streamlined using the G76
threading cycle. The core to automating this is the H parameter
(number of thread starts) or using successive passes with a calculated
Z-axis shift, depending on your specific version's recent feature
update.
If your version fully automates it, your block will look similar to this:
gcode
G76 P0.5 Z-20.0 I-0.3 K0.4 F3.0 H6 ...
Use code with caution.
• F (Feedrate/Lead): This must be set to the total Lead, not the
pitch. (e.g., if Pitch = 0.5mm, then F = 3.0).
• H (Starts): Set to 6. LinuxCNC will automatically index the
spindle's index pulse by 60° increments for each start.
That is cute, but for 2 starts, I just ran the no reverse of the normal
command to make the restart/retrace. G76 doesn't even get used. I goto
end from start of both B & Y, stop, raise Z, B has been rotated around
70,000 degrees, rotate B an additional 180 degrees & drive Y back to
start while going to 180 B. Which in this case is off the end of the
stick. Increment Z & Y to follow the polygon & repeat till the thread
is cut. B is doing around 150 rpm. Air is on to blow dust away. I
make the nuts in openscad, two passes at double pitch, 180 degree
separation, nuts fit using essentialy the same polygon tooth shape for
a 6mm by 4MM tall buttress thread. Spindle motor mounted on a printed
plastic wedge for the 7 degree load face with a std 1/16 RN tool with a
.25" DOC. I'm not allergic to modding the machine as it needs
additional Z clearance so the Z clears the dead center at that end of
the Y travel.
I have quite a few routines that do use G76, will they continue to
work? If not, I'll vote no.
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