BP Mill Quill Lock and Z inhibit

The physical mechanicals of uncoupling are done. I don't need help with that.
The motors are SEM servo motors that came with the original anilam control. The control has been replaced with a pc running linuxcnc and mesa hardware. There is also no separate DRO. I'm reading position off the A10 linear encoders on the x,y and rotary encoder from us digital on the Z screw. No additional linear encoder on the quill.

If it is a servo, you can use the pin "pid.N.enable" to disable the pid loop for one axis. That would make the analog output to that drive zero. With a velocity mode servo drive that should cause the motor to "stop" and be "locked" up with the drive still enabled. But this could easily result in drift or a low speed run away. If linuxcnc is disabled before you return the normal control of the Z pid enable. It should not cause a jump in motion. You may need to do something with following error settings to prevent alarms.

Thanks Todd. If I use pin "pid.N.enable", will linuxcnc limit any motion to that pin if I inadvertently hit the jog keys or rotate the mpg for that axis or have a g code ready to move that axis? What about turning off the input side of that axis like the jog and mpg so not to trigger a joint following error? Does that make sense what I'm asking?

It will not send ANY commands to the analog out pin. This is why it is little dangerous. If the drive starts to drift or runaway, Linuxcnc will not be able to send any corrective commands.

I'm coming down the home stretch on this retrofit...sorry to keep pestering you with a billion questions. One moment I feel like I'm understanding something the next I'm back to square one.

I'm trying to implement latching the pid.z.command input that was suggested above. I need to configure this correctly as I can't afford a runaway on the z. I don't think I'll be quick enough to hit estop on such short travels. I'll park it in the middle before trying the code and switch. I do have limits installed but hardly any over travel.

Anyways, I started with this which I know is not correct and need some guidance in completing it:

# --- manual Z-QUILL-LOCK ---
#net z-quill-lock <= hm2_5i25.0.7i77.0.0.input-14

loadrt mux2 count=1
addf mux2.0 servo-thread

net z-quill-lock mux2.0.in0 <= axis.z.joint-pos-cmd
net z-quill-lock mux2.0.in1 <= mux2.0.out
net z-quill-lock mux2.0.sel <= hm2_5i25.0.7i77.0.0.input-14
net z-quill-lock mux2.0.out => pid.z.command.input

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No I got an error. I'll have to re-load to see the specifics. I don't remember what it was.