For a project I was building, I had to drill a centred hole in the end of several 12mm dowels. To keep all of the holes consistently centred, I made this simple jig for my plunge router.
MAKE THE JIG. The body of the jig is just four pieces of plywood glued together with a base made a little larger to act as a clamping surface. The holes in the centre of the jig are sized to accommodate the dowel and a router bushing, as shown above.
USE THE JIG. Start by clamping the dowel in a vice. Place the jig over the end of the dowel until it stops. With a bushing attached to the router, plunge a spiral bit into the end of the dowel to drill a centred hole.