I had my z home setting at -4.5 still not sure why.Now I lowered my router how do I know what to set it at now

Hi,
most people have their Z home right at the top of travel. It means the machine co-ords of all your machining/engraving is done
at negative machine co-ords. Sounds weird I know but it works out well.

Lets say you do that and home Z at top of travel. Load a piece of work and jog downwards (increasingly negative machine co-ords) until
the top of the material. Now zero Z. From here on the top surface of the material is 0, a negative number say -1.5 is 1.5mm deep into
the material and any positive number say 2.0 is 2mm above the material and its safe to rapid to a new location or whatever.

Craig