Today, I learned to solder. There were quite a few wires to solder. Each axis has two emergency stop switches, and each of these had at least two wires. I also put in a panic button. If things go bad, all I need to do is push the panic button to cut off the mill's DC power.
With all the stops wired and in place, I ran each axis until it triggered its stop. It worked! The motors each stopped running. I could no longer move them through the software, but I could turn the screws by hand - but only a few turns until the switches clicked off and the controller locked the motors in place. Turns out these positions (smidgens away from triggering the emergency stop switches) were excellent choices for the axis zero settings.
The other thing I learned today was how to write the control code, called G-code. It was very cool to write a line of code, send it to the controller, and see the machine behave exactly as expected.