Locate shelf-pin holes in a snap

When I build shelves, I want them adjustable, and the most effective way to do that is with shelf pins. But getting perfectly repeatable results is challenging unless you use an indexing system. To remove the risk and virtually eliminate measuring, I made this see-through indexing jig to create perfectly spaced ¹⁄₄ " shelf-pin holes by the bushel.

The key to the jig is the spring-loaded pin, which snaps down into the previously drilled shelf-pin hole to ensure positive location. I made the pin by cutting the head off a ¹⁄₄ x3" bolt and then grinding a slight taper on the non-threaded end. Next, I drilled it and inserted a ¹⁄₁₆ " roll pin in the rod to compress the spring. You can make the jig housing as shown with almost any material, but I used ¹⁄₄ " acrylic for the top and bottom, as shown. It provides a slick surface and allows me to see the previously drilled hole.

To use the jig (as shown, it spaces holes 1" apart and 1¹⁄₄ " on center from the edge of the workpiece), set your drill press fence 1¹⁄₄ " from the bit center, and drill the first hole. Next, place the jig over the workpiece so that the pin snaps into the hole. Move the workpiece and jig together along the fence until the drill bit fits perfectly into the bit-index hole in the base, and then clamp the jig to the fence. Once attached to the fence, it will now "float" over the workpiece, so you can drill a hole, lift the pin, slide the workpiece along the fence until the pin snaps down into that hole, drill, and repeat.
—Vell Holcombe, Milton, Penn.