We may receive a commission when you use our affiliate links. However, this does not impact our recommendations.
My beam compass is perfect for drawing huge arcs. It’s super easy to make, and I can adjust it quickly without using screws or clamps. To change the arc’s radius, I just slide a saddle-style head along the beam.
Make the beam from a piece of hardwood. Mine is 1″ x 1-1/4″ x 36″, but you can make it any size you want. Make the sides of the sliding head from 1/4″ plywood, and the bottom from 1/2″ or 3/4″ plywood. The head should fit snugly on the beam, but still be able to slide. For the pivot point, I drilled a hole in the head’s bottom and inserted a dowel center. (A nail would work just as well.) Drill a hole in the beam’s other end to hold the pencil. –Larry LaBeau
