USB/Ethernet controller for Mach3/4 advice

[EddyCurrent]

I'm helping a friend converting a mill and all this servo stuff is new to me, so I still have a lot of questions I cannot find the answer here..

What is the best approach for homing? Using micro-switches and the encoder z output? Or there is no need for accurate homing.

How to wire the e-stop? For steppers I cut the power to the motor but here I have e-stop input at drives as well as controller. If I use the e-stop this way, the machine will not lose its position, and I can continue the work without homing the machine. Am I right?

I've used encoders many times but not in the context of cnc machines. As I understand it, homing works as you suggest, the switch detects the gantry approaching home and tells the system to start counting the encoder pulses to actual home position.

Regarding e-stops, most people would kill the power if an e-stop was activated because it's an emergency situation. If you want the machine to stop you should use a 'Stop' button instead.
Either way if power is left on to the encoder and Mach3 for example then the position should not be lost. If the encoders are absolute as opposed to incremental then they will always know their position even if the power has been off. As I mentioned this is how they work on equipment I've used in the past, maybe wait until a cnc user replies for more appropriate info.

[paulus.v]

Thanks Eddy, I think most of the encoders are incremental and some sort of homing is needed. As I understand, in the switch based homing, when the switch is triggered the encoder goes to Z which is one pulse per revolution. If one rev. =1.5mm movement, I assume that a switch repeatability of less than 0.75mm will do the job.

On my stepper based CNC the limit switches are wired in series with the e-stop and cuts the power to both spindle and steppers, not the electronics and triggers in mach3 an e-stop to pause the g-code. But with servos if both the drives and the controller have an e-stop input, which means double protection, is there any need to cut the power?