Guess What? 35

It’s the inside of an old fashioned Cylindrical (planetary) pencil sharpener!”

Cylindrical Sharpeners

A larger, sta­tion­ary me­chan­i­cal sharp­ener can be mounted on a desk or wall and pow­ered by a crank. Typ­i­cally, the pen­cil is in­serted into the sharp­ener with one hand and the crank turned with the other. This ro­tates a set of he­li­cal cylin­dri­cal cut­ters in the mech­a­nism, set at a di­verg­ing angle to each other. This quickly sharp­ens the pen­cil, with a more pre­cise fin­ish than the sim­pler blade device.

Ad­vanced mod­els have a spring-dri­ven holder for the pen­cil (the pen­cil ad­vances into the mech­a­nism while being sharp­ened). Some ver­sions also offer a reg­u­la­tor of the de­sired sharp­ness (it is not al­ways de­sired to make the graphite core nee­dle-sharp).

Such sharp­en­ers may be very easy to use even by chil­dren, but may be more ex­pen­sive than prism sharp­en­ers. Some such ro­tary sharp­en­ers have only one burr cylin­der. The cas­ing of the sharp­ener is the repos­i­tory for the pen­cil shav­ings, and needs to be emp­tied pe­ri­od­i­cally. These mech­a­nisms are also called plan­e­tary sharpeners, in ref­er­ence to their use of plan­e­tary gears.

Credit: wikipedia.com

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