I wouldn't recommend less than three inches of Z clearance to the table top unless you know for sure it will only be used for 3/4" and thinner materials. You need room to have a removable dust shoe and clearance to change tools. Z axis travel needs to be able to have the router/spindle reach the table with a short cutter, and to retract the long cutters to at least just above the lowest fixed point of the Z assembly. Being able to raise it any higher is just making it easier to change cutters. You can't cut anything if the cutter is above the Z assembly clearance. My smaller machine has 2-1/2" clearance to the spoil board and I need about 1/2" more clearance for some projects. My big machine has 6" clearance and 8" travel. It was intended to cut 5" thick material for molds.
CarveOne
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