Hi
once you have once you have set your Z zero for the tool ( and I assume you have also established your X and Y origin or WCS, then you can just jog the Z axis up and connect your dust hood, and regenerate with new values. but if you would like it to have a fixed distance that is automated, then check that panel to the left of your touch off GUI. The second variable you can set Retract Distance default value is set at .1 in my case I'm using millimeters so you will note that normally when you 0 your tool it's rises 0.1 (of an inch or a millimeter just enough to get your your gauge block out. If you want it to move the spindle up 75mm (3") then set it there. But keep on top of the settings. And you can also refer to the PDF document in the Root Directory in your "C" drive for Mach4 Hobby and look in the Docs folder. There you'll find Touch off Help
if I haven't answered your question then let me know
best regards,