For setting precise plunge depth on my router, I often use a gauge of the same thickness as the desired routing depth.

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Micro-Adjust Plunge

For setting precise plunge depth on my router, I often use a gauge of the same thickness as the desired routing depth. You can use almost anything for a gauge: a piece of scrap or a drill bit that's the desired thickness or diameter.

First, lower the motor and bit until the bit just touches the benchtop. Then lock it in position. Place a gauge on top of the turret stop, lower the plunge router's stop‑rod down to the gauge, and lock the rod in place. When I remove the gauge and unlock the plunge mechanism, the router is ready to plunge to the correct depth.

Need to rout just a smidgen deeper? I reset the stop rod using the same gauge and an automotive feeler gauge to fine-tune the depth.
—A. C. Bouchard, Peabody, Mass.