The pencil “lead” is actually a mixture of graphite and clay. More clay in the mixture makes the lead harder. A harder lead has a higher number. Pencils are numbered from 1-3 but most people use a ...

Common mechanical pencils come in sizes to accommodate 0.5, 0.7, and 0.9 mm leads, but there are bigger and smaller ones available. Perhaps one of those really large drafting lead holders could be ...