The peppermill that resides on our kitchen table was on its last legs, so my wife bought me a new one for Christmas. It seemed reasonably well made, had an adjustment for how fine it ground the pepper, and even had the grinder at the top so it didn’t leave a mess wherever it sat. I was a little concerned that the grinding surfaces were plastic, but I’ve learned over the years that well-chosen polymers don’t necessarily mean cheap. A couple of days later, it stopped grinding -- OK, maybe it was cheap after all.
Now that I had two barely functional peppermills, I did what any engineer with four kids would do -- I set them aside for some time when I could figure out what was going on. A couple of months later, having exhausted the supply of pre-ground pepper in the house, the time had come for a design review. I carefully disassembled the peppermill and examined its components. It was set up as a ratcheting design, where the grinding rotor (white) was rotated by engaging teeth on a driver (black square).
A close-up look at the ratcheting surfaces of the peppermill.
The square driver was inside a square recess, which was driven by the outside of the mill, held by the user. A curved disk spring pressed the square driver against the grinder. The teeth that engage between the driver and grinder were shaped such that they would engage solidly in one direction, but float up and over each other in the other direction, providing a ratcheting action so that an oscillating rotation of the peppermill body by the user would create a continuous rotation of the grinding surface. The diagnosis was obvious: the spring was not strong enough, allowing the mating teeth to float over one another in both directions, and not turning the grinding surfaces at all.
The first attempt at a solution was to bend the spring, to cause a slightly greater engagement force. After reassembling the peppermill, I found that its behavior had not changed. Only brief contemplation was required to realize that the ratcheting action was a feature I could live without. So I once again dismantled it, and filled the square recess the driver floats in with hot-melt glue, making for a very stiff spring indeed. It no longer ratchets, but it does grind peppercorns just fine. I wonder if the grinding surfaces were touching initially, causing me to damage the form on the engaging teeth on first use, or if there are untold numbers of inoperable peppermills floating around out there. I retained the old one with the metal teeth as a backup in case the plastic grinding surfaces don’t last; it will be harder to repair because of accumulated damage from combined fatigue (use) and impact (dropped too many times) damage.
This entry was submitted by James Sebastian and edited by Jennifer Campbell.
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