Z axis loses zero

Would the offset be in the GCode or in LinuxCNC?

If you type in g49 in mdi what happens to the position readout?

It sounds like after the tool change completes it calls out g43 tool height offset

Here is outcome of checking g49 and g43.

1. Zeroed Z axis. DRO read 0. Loaded G-coded.
2. Started file (play button in UI).
3. Tool change dialogue appears. I choose okay (cause I do not need to change the bit...would love to get rid of this tool change)
4. Bit proceeds to dive into the work piece (3/4" wood) a 1/2". It should only be going in about an 1/8" (vcarve operation)
5. While at this too far plunged depth, G43 read 0.1595 (yeah it was well below this depth) and G49 read -0.4567 (more likely where the bit was at).

For step 5, I used MDI and the DRO with the program stopped and without moving the x,y,z axis.

Gcode that had run up to my stopping the program (using the Stop button in the UI):
%
(1001)
(T1 D=0.75 CR=0. TAPER=45DEG - ZMIN=-0.1427 - CHAMFER MILL)
N10 G90 G94 G17 G91.1
N15 G20
N20 G53 G0 Z0.
(ENGRAVE2)
N25 T1 M6
N30 S20000 M3
N35 G54
N40 M8
N45 G0 X1.087 Y-5.076
N50 G43 Z0.5 H1
N55 G0 Z0.2
N60 G1 Z0. F39.37

Check your tool table. Are there any offsets in there?

BobsGotCnc wrote: Sometime when jogging my Z axis goes up it makes that grinding/pushing noise while the lead screw does not move. It does not do this going down. I can eliminate this behaviour when going up by apply a very minimal pressure

This sounds like a weak stepper, or driver.

Try increasing the Z axis driver current, if you can. Monitor the motor temperature (but be aware that "uncomfortably hot to touch" is well inside the operating envelope of a stepper motor.

Also try reducing the max acceleration (especially) and the max velocity of the Z axis. You might even be able to _increase_ the velocity if you drop the accelleration.

The Tool Table was the solution. In there I found the Z offset that keeping getting applied. Cleared it out, and things the two operations I did today went well.

Thank you.