Editor’s note: Here is one of the coolest Tricks of the Trade from our December 2006 issue from reader Rick Wilson of Houston, Texas.
Setting the projection of a router bit using a ruler can be problematic, and not terrifically accurate, especially if your eyes aren’t what they used to be. To solve the problem, I made this simple but very accurate router bit depth gauge from a scrap of wood and an inexpensive dial indicator ($15.50 from Lee Valley, 800-871-8158). It measures bit projection in thousandths of an inch up to 7/8″, which is enough for most of my grooving and slotting tasks.
The dial indicator shaft fits snugly into a hole drilled in the top of the inverted U-shaped gauge block. A slot extending out from the hole is pinched together with a machine screw to lock the indicator in place. After unscrewing the stock tip, a small hardwood block is friction fit onto the end of the plunge rod to serve as a plunger pad.
To use the gauge, first zero it out with the plunge-rod block pressed against the router base or router tabletop. Then center the block over the bit, and raise the bit until the desired projection is reached.