How a pencil sharpener works · OakCrest Academy

✏️ How a pencil sharpener works

Inside the body is a conical hole (shaped like a cone): wide where the pencil enters and narrowing to a point at the back.
A hardened steel blade is screwed over a slot in the side of the cone, so its edge lies exactly along the cone's surface.
As you turn the pencil, the edge shaves off a thin curl of wood, and the pencil is drawn a little deeper into the hole.
The hexagon's corners are cut first; then a smooth wooden cone forms, and finally the graphite core is cut to a point.
The point always takes the angle of the hole (22 degrees in this sharpener), so further turns only make the pencil shorter, not sharper.

New words

cone: a solid that tapers smoothly from a circular base to a single point
blade: a thin, hardened strip of metal with a cutting edge
angle: the amount of turn between two lines that meet at a point, measured in degrees
graphite: a soft form of carbon, mixed with clay to make the pencil's core
shaving: the thin curl of wood the blade removes

🏠 Try it for real

With a grown-up, examine a hand sharpener: find the screw that holds the blade and observe how the blade's edge lines up with the cone. Then sharpen a pencil, counting your turns, and measure how much shorter it became.

💭 Talk about it

Why does a pencil become shorter every time it is sharpened, and where does the missing length go?

Now explain it back: point at each part and say what it does.