Things to consider Lead size/thickness A mechanical pencil takes only one lead size. 0.5 mm and 0.7 mm are common; go thin if you write small, thick if you press hard.

Lead pencils were now about to make their mark. In 1609, a character in Ben Jonson's play Epicoene describes some mathematical instruments including "his square, his compasses, his brass pens, and ...

Carbon nanotube pencil leads used for drawing sensors onto paper By Ben Coxworth October 10, 2012 MIT has developed pencil "leads" that can be used to draw gas sensors onto paper View 1 Images ...