Spindle Synchronization to pick up existing threads

Hello,

I'd like to try to pick-up on existing internal threads on a part I'm machining using the G76 (or a programmed version of G33 if necessary) threading code and cut them deeper after failing my first attempt. Is there a way to run one pass to visually see how well it lines up to existing threads, pause the program, jog the x or z axis to compensate, and then run another pass or continue without losing synchronization? I'd appreciate any support.

Regards,

SG.

So even if I stop and start the threading program (or open a new program with the same pitch), it won't lose spindle synchronization? It will start cutting at the same location assuming I don't change anything?

Does that mean Linuxcnc initiates threading at the same spindle encoder pulse count whenever a threading program is started and it keeps that value in memory as long as Linuxcnc is running?

Ah... OK, that makes sense.

Thanks for your input. It's much appreciated.

stegrg wrote:

So even if I stop and start the threading program (or open a new program with the same pitch), it won't lose spindle synchronization? It will start cutting at the same location assuming I don't change anything?

Correct, the system is as consistent and repeatable as the given homing basis. If the homing is consistent/repeatable across sessions, then the action will be too. Since in your case the spindle angle is homed from the spindle index, precisely and absolutely, this makes it consistent/repeatable across sessions. If the other axes, fixtures, toolholding, and workholding are likewise precisely/absolutely homed, then the whole works remains consistent and repeatable across sessions, including shutting down and cold-starting the machine.

If you lose the homing on the workpiece (such as you take it out of the fixture), then you have to somehow home it again, such as by "touching off" in the case of linear axes, or by in effect "touching off" (usually spoken as "picking up") the phase timing of threads in the case of threads. This "picking up" is executed by either manually rotating the workpiece in the fixture, or tweaking the Z touch-off, while you microscopically inspect the threading tool point against the previous thread work. It's no different than linear touch-offs, just trickier because it involves the angular C axis interacting dependently on a linear Z axis.

if it is setup as you say it will only fail if the mashine powers off
but there is a manuell way to step into the tread
if it is that bit to work on 2 Days

You shoudt always finish operations like this in one Flow

Thanks everybody for the feedback. I managed to get it synchronized and cutting again this morning.