So, part of the fun of my new bookshelf project is to cut a series of evenly-spaced dadoes into two side frames for each shelf that are parallel and evenly spaced from the floor.  No easy feat considering that the two frames have sloped fronts as they slope back from the wider base to the narrower top.

What I needed was a way to cut a consistent groove across the inside faces that would be easy and easy to repeat. Enter the Dadonator – OK, it’s a fancy name for a two scraps of plywood – a 3/4″ and a 1/4″ piece I could stack together to give me  a wide base to lay across the frame that would give a great base for the router to ride over.

The two sheets had to be stacked together to give me the right height above the workpiece to use my secret weapon, a 1/2″ diameter pattern bit.  With the straight edge of the ply for the bearing to ride against, giving me a straight dado.  And, with this being a flush trimming bit, I could lay the plywood sheets against the layout lines, clamp them in place and route away.

The result are very clean dadoes lining up exactly across the frame pieces ready for me to do the next step – tackle my shelf glue-up demons!