Cutting a tapered thread with G76

I am baffled with how the tapered thread command of lcnc works. I have a 16mm Id thread, the last half of the thread is in a collet that is clamped causing the thread to be deformed and tapered , smaller on the back end. I'd like to program the taper out, which on fanuc lathes was a an I value, which was the dia distance between the minors at either end of the taper.
I need to program about .003 on the dia over and inch.
My present command
G76 P.059K.075I-.01Q0 H3
How is this done?

You can't (currently) do a constant-taper thread with G76.

But it sounds like you only need an exit taper?

linuxcnc.org/docs/2.7/html/gcode/g-code.html#gcode:g76

E and L control the taper, but only the distance over which it occurs. It is always a taper from full depth of thread to zero depth of thread.

If you want a straight taper then you can use G33 and programme each pass separately.

Or there is this experimental work (and discussion)
sourceforge.net/p/emc/mailman/emc-develo...any.com/#msg35333774

Hi

Has this been resolved? Can Linuxcnc do tapered threads with G76 now?

Thanks,

I don't think anything further has happened You could try joining the conversation on the mailing list. The multispindle letter clash has been resolved now.

Bump...

Can LinuxCNC still not tapered threads?
Mark

You can do it with G33

I don’t know what happened to the tapered G76 work.

Thanks for the quick response Andy,

Bummer. Now I have to write a subroutine to do it with G33, and you have seen how careless my code is I will take me an hour to write it and two to debug. Good practice.
Mark

Just wondering if this was ever resolved as I need to cut a 1/8-pipe thread on some parts? (tried a 2 line G76 but it complained about missing move axis)

Thanks
M

I don't think I've ever used a G33 in my life...
I need to make a 1/8-27 npt go up and then become a 5/16- 24 straight so maybe it's time to learn
M