Large Circle drawing Trammel Points

thingiverse

Update: To avoid confusion about imperial units, I've uploaded STL files with dimensions in millimeters. Trammel points for larger circles can be created without limits, as long as the steel rule used is sufficiently long. To accommodate frequent requests to draw and cut out larger circles and arcs that exceed my template availability or compass size, I designed this fixture. The radius setting on the drawing point can be read directly from the scale on the front of the pencil holder. With a minimum radius of 1.25 inches, users can create a wide range of circle sizes, up to the length of their steel rule. A Pentel P205 (.5mm), P207 (.7mm), or P209 (.9mm) mechanical pencil is used as the drawing instrument on the drawing point. A 1-inch nail with its head cut off and friction-fit into a receiving hole in the fixture serves as the pivot. The hardware required for assembly consists of 8-32 nuts and screws. Initially, I considered using thumbscrews for the pencil end but found it easier to adjust using a screwdriver instead. By backing off the screws slightly, users can achieve a good friction movement.