copper tube mechanical pencil

thingiverse

This is a mechanical pencil I designed to fit a 10 mm OD by 7mmish OD copper tube approximately 156 mm long. It works by shaking the pen, causing the 3 mm hole marking graphite to move outwards. A spring and a metal slug measuring about 49 mm x 6 mm are required for its operation. This prototype was made from wood and scrap metal, with plans to update it once printed parts become available. Update: The parts have been printed, and I've superglued the tip in place. However, I suspect that the tube may need to be slightly longer due to difficulties encountered when working with the graphite at its fully retracted position. To assemble this mechanical pencil, simply drill holes of approximately 3 mm in diameter and sand them to a precise fit. Use one of the burs left behind by the pipe cutter to hold the tip piece securely in place.