X,y and Z zero zero for free on Mach3
 

At http://www.cnczone.com/forums/showthread.php?t=56079 is a thread on a screen set that incorporates a X,Y,z zero plus edge finder. here is a brief install procedure.

In step 3 go to the Artsoft link and run the install. This gives the MachBlue screen set. This does not give the feature. Next go to the link on cnczone and download the file. Make sure that the file downloaded is the same one listed in instructions. For some reason I got the wrong file on several attempts. Unzip the file and copy the files into proper directories. Now follow instructions on starting MachBlue screen. As to the fixture I think that a rectangular one 1" or 2" thick would be better. This would allow the same fixture to be used for centering and edge finding.

Go in Mach3 and go to Config/General Configuration and uncheck Enable Tool Change. Now when a tool change is seen in the code the Z axis will go to the tool change height and spindle will turn off. Replace tool, place the fixture under the tool and click on Z set. Tool will move down till it touches the fixture. The fixture off set will be pluged into Z as zero point and tool will raise.25" above fixture. Remove fixture and hit Cycle Start. Spindle will turn on and job will contunue.
Been using it for several days and it is really fantastic!