On my CNC router, the home switch for the Z-Axis is at the top. After clicking "Ref All Home" button, I move the Z-Axis so that the router bit touches the workpiece and zero the program coordinates. If a project requires two or more router bits, I have to reset the Z-Axis. Sometimes, the depth of cut is wrong. Let's say that I run a program to do pocket cuts at 1/4" using 1/8" router bit and then run another program to do profile cuts at 3/4" using 1/4" router bit. Even after moving the Z-Axis so that the router bit touches the workpiece and zeroing the program coordinates, the profile cuts are 11/16" deep instead of 3/4" deep. I can't zero the machine coordinates after changing router bits. How do I zero both program and machine coordinates after changing router bits and moving Z-Axis?