I recently realized that if I push up on my spindle, it can move up by pushing the motor coupler apart. The lovejoy / spider coupling wasn’t meant to hold together when the rods in either end are pulled apart. This is good, in a since, in that there is a limit into how hard the Z motor can push the bit into the material, but it also means that I might have a variable depth of cut that doesn’t quite make it to the depth I expect, especially with a downcut bit.
I just replaced the coupling with a diaphragm coupling in order to have more precise control over depth of cut:
I’ll see how this works.