Although most people I know use mechanical pencils, traditional wooden pencils are still as important today as when they were first introduced. Wooden writing utensils are still used in compasses and colored pencils which means they will continue to need sharpening. Before receiving this prompt, I never realized how complex a simple wall or desk mounted sharpener really is. As a kid, I would utilize the class sharpener to avoid boring lessons or to talk to my friend but didn’t know the engineering involved to make such a device work. I’m not talking about an angled sharpener but rather a planetary sharpener like shown below:
Planetary Sharpener with External Case Removed. Photo Credit: Wikipedia.org
Planetary sharpeners installed in classrooms or offices in the 60’s can still be found in fully functional form. These things were designed to take abuse, misuse, and to stand the test of time. Taking a look at a mounted sharpener I was able to come to three engineering conclusions…
- Planetary Sharpeners must be designed for ease of use
It’s safe to assume that a sharpener is going to be used by both adults and children at some point in its life cycle. This means that a designer needs to ensure that a child can apply sufficient force to crank the mechanism with ease. If this condition isn’t met then the market for such a product would become limited to adults working in office settings.
- Material selection is key
As stated above, planetary sharpeners can be found in perfect working order even in run down and abandoned buildings who have gone years untouched. I attribute this to great material selection. Most sharpeners are manufactured out of steel which has been hardened to resist wear and deformation.
- Planetary Gearset
Lastly, if you have ever taken the case off of a mounted sharpener, I’m sure you’ve seen the cutting cylinders used to sharpen. The internal mechanism is basically a planetary gearset. A sun gear is usually centered in the middle of the train with planet gears connecting it to an outer ring. This allows the center of the outer ring to revolve around the center of the inner ring or vice versa. In the case of a sharpener, the inner sun gear is replaced with the pencil and the connecting planetary gears are replaced with rotating cutting cylinders. These helical cylinders are designed to cut and are angled to form a point which also forms the point of a pencil. More information about planetary gears can be found here.
Planetary Gearset. Orange Sun Gear, 3x Teal Planetary Gears, and Blue Outer Ring Gear. Photo Credit: Reddit.com
Whether it be a door handle, a cup, or even a pencil sharpener, it’s sometimes easy to dismiss the complexity of our everyday products. The beauty of engineering is taking a complicated task and making it routinely easy for anyone to do.
Until next time!
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