Although I am thankful that I entered the engineering profession after CAD was invented and have never had to complete a part drawing by hand, I admire the technical drawing skills that used to be a requirement in the industry. They can still be very helpful for quick ideation and communicating concepts, and as part of my effort to improve my drawing ability I decided to build my own drafting arm.

There used to be many different designs for drafting arms/machines, but I opted for this relatively simple setup comprised of two 4-bar linkages. These ensure the end of the arm is always parallel to the edge of the table, and the angle of the rulers can be adjusted using the knob and associated markings. Most of the parts are 3D printed with M4 hardware and heat-set inserts being used for assembly. I came up with a few different designs, but eventually landed on a setup with all the hardware hidden that gave the arm a clean look. Most of the challenges involved tolerancing of the joints and the angle locking mechanism I designed, but a bit of iteration got rid of any slop in the linkages.