The Window Lucy Asked For

On going from plastic to sapphire because compromise felt wrong

The Mikros One has a sapphire crystal window in the hopper lid, held in place by a ring of tiny screws. It's the kind of detail you'd find on a luxury watch case back, not a coffee grinder.

It exists because my wife wanted to see the beans, I tried plastic, and it looked and felt terrible.

The Problem: Beans Falling Out

The early prototypes had no lid at all. Just an open hopper. Fill it too full, tip the grinder, and beans would scatter across the counter. Not ideal.

So I added a lid. Simple aluminium disc, hinged to stay attached, same reason the crank folds. I'd lose it otherwise. Solved the spilling problem. Created a new one: you couldn't see how many beans were left without opening it.

My wife used the grinder one morning and said, "I want to see the beans."

Fair point.

The Plastic Solution (That Wasn't)

First attempt: transparent plastic window in the aluminium lid. Functionally adequate. Visually awful.

The plastic scratched immediately. Within a week it was cloudy from micro-abrasions. It cheapened the entire grinder, all that work on silicon carbide bearings and 7075 aluminium, undermined by a foggy plastic window that looked like it belonged on a kitchen gadget.

I tried different plastics. Polycarbonate, acrylic, various formulations. They all scratched. Some worse than others, but none acceptable for something you'd handle daily for years.

I could have accepted "good enough." Most manufacturers would. But my father taught me that tools you use every day deserve better than compromise.

So I swung the other way entirely.

The Sapphire Solution

Sapphire crystal. 9H on the Mohs scale, harder than anything except diamond. Scratch-resistant to everything you'd encounter in normal use. Perfectly transparent, stays that way indefinitely.

It's what watchmakers use. My father's Seiko, passed to me, then to my son Oliver (my co-founder)—, has a sapphire crystal. My Maurice Lacroix has one. Every watch I've ever admired uses sapphire for the same reason: it stays clear.

I'm a wannabe watch collector. I don't collect because family comes first, before spending thousands on timepieces. But I study them. Jaeger-LeCoultre is my passion brand, the Reverso, the Master Control, the way they approach engineering and finishing. I can't afford them, so I admire from a distance.

But I understand why they use sapphire. And I understand the mechanical retention systems that hold crystals in watch cases, not glue, not snap-fits, but precision-machined bezels with tiny screws that distribute clamping force evenly.

If I couldn't own a JLC, I could at least build a coffee grinder with the same approach to materials and assembly.

Why Tiny Screws?

The sapphire crystal sits in a precisely machined recess. A retaining ring holds it down, secured by small screws around the perimeter. Each screw applies even pressure, preventing stress concentration that could crack the crystal.

It's the same principle watch case backs use. Not because it's the cheapest method, adhesive would be simpler. Because it's serviceable, it's elegant, and it distributes load properly.

You can remove the retaining ring if needed (though you probably never will). You can see the screws, tiny, evenly spaced, deliberately placed. It looks intentional, considered, like someone cared about how the parts went together.

Because someone did. I did. I care.

Form Following Function (And Passion)

The sapphire window works because:

• Scratch resistance (stays clear indefinitely)
• Optical clarity (you can actually see the beans)
• Durability (won't craze, yellow, or degrade)
• Mechanical retention (serviceable, even load distribution)

It looks like a watch component because I used watch assembly principles. Not as marketing theatre, because that's how you retain a hard, brittle crystal without cracking it.

Could I have used hardened glass? Yes. Would it have worked adequately? Probably. But adequate isn't the standard when you've spent years studying how JLC assembles movements and finishes cases.

My wife wanted to see the beans. Plastic was inadequate. Sapphire with mechanical retention was the right answer, even if it cost more and took longer to engineer.

The Honest Position

The sapphire crystal window exists because:

1. My wife wanted to see the beans (practical request)
2. Plastic looked terrible and scratched immediately (failed solution)
3. I studied watch construction and understood how to retain sapphire properly (knowledge)
4. I refused to compromise on a detail I'd see every day (choice)

I won't claim this was "inspired by the world's finest watchmakers" when the real story is: my wife asked for a window, plastic was unacceptable, and I used what I learned from studying watches I can't afford to buy.

The sapphire crystal and tiny screws aren't tribute or homage. They're the application of watch assembly principles to a coffee grinder because that's the engineering I admire, even if I can only afford to own two watches, one inherited, one saved for.

Passion for Machines on a Wrist

Horology isn't really about timekeeping anymore. Quartz keeps better time than any mechanical watch. Horology is about appreciating machines on a wrist—tiny, precise, beautiful mechanisms doing something complicated within strict constraints.

I can't afford to collect them. But I can study them, understand them, and apply those principles to things I do build.

The Mikros One has a sapphire crystal window because my wife wanted to see the beans, and I couldn't accept a foggy plastic solution when I knew how watchmakers would solve it.

Family comes before watch collecting. But that doesn't mean I can't build coffee grinders the way JLC builds watches.