We might get closer to a right answer if we knew the zero setting on what? I immediately thought of Incra positioner, John seems to have a thought on something else, could be a Wixey angle cube, depth of cut, distance from center...
@stan herman - welcome to the forum. More details would certainly help, but I'll guess that you want to zero out a bit on a plunge router. If that is the case, plunge the bit down until it reaches the top of your material, that's the zero setting. Then, using a brass bar or something similar, lift the bar near the scale and above the turret, by the amount you want to plunge the bit down. Then when you plunge the bit will plunge down by that amount. You can use several steps on the turret to reach your level as you don't want to plunge too deeply at one time.
Hope this helps, if not please explain what you are trying to do.
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