People blame themselves, or the sharpener. Usually neither is at fault.

How a pencil is made

Two slats of wood are grooved, a core is laid into one, glue is applied, the second slat is clamped on top, and the block is then milled into individual pencils and lacquered.

Everything that matters happens in that glue-up. The core must be bonded to both halves and sit centred in the barrel.

What an unbonded core does

If the core is loose in the groove, the wood flexes independently of it every time the pencil is used or dropped. The core fractures at intervals along its whole length, inside the barrel, where you cannot see it.

Then every sharpening exposes a fresh break. The pencil is not breaking because you sharpened it; it broke weeks ago and you are only now reaching the crack.

What an off-centre core does

Sharpening reveals more wood on one side than the other and the point comes out lopsided and weak. Press on it and it snaps at the shoulder.

You can see this one: look at a sharpened point end-on and check the core sits in the middle.

What you can actually control

Buy pencils with a bonded, centred core, and use a sharp blade — a blunt rotary sharpener tears rather than cuts and will break even a good pencil.

Beyond that, dropping pencils point-down onto a hard floor genuinely does damage the core. It is the one user error in this list.