Process: drawn arc to contoured board


Over the past couple of weeks I took some snapshots as I worked out a process in the woodshop, a problem I was puttering on a few hours at a time: how to turn an arc drawn on my workbench into a long board, contoured with that arc. The solution seems laughably complicated. But the result is very accurate and looking back over it, I can’t think of an easier way to get it done.


Draw an arc.


Make a solid section of the cylinder defined by the arc.


Make a solid section of the negative space excluded by the cylinder.


Make a rigid sled with sides to constrain a router, and with the negative section at its short ends. Place the sled on a base with the positive section at its short ends.


Make rails to keep the movement of the sled aligned along the arc.


Attach a long board to the base.


Mount a router in the sled. Mill away the entire top surface of the board.


This process will generate a curved board and many wood shavings.


The contour of the board’s curve will match the arc drawn at the beginning of the process.