How Does a Mechanical Pencil Feed Its Lead?

Why does the lead move forward in small steps when you press the button, but stay put when the spring pulls the mechanism back? Follow one simplified click-type mechanical pencil through its split chuck, clutch ring, return spring and friction retainer near the tip.

The chuck first grips and carries a single piece of lead. Near the end of the stroke, the ring stops and the jaws open. During the return, a light retainer holds the lead until the jaws grip it again. The cutaway and the no-retainer comparison are teaching illustrations; they are not a force simulation or a specification for every pencil. Movement and clearances are enlarged so the sequence is readable.