The Moccamaster KM5 is a nice grinder with one oddly polarizing detail: the front switch.
Unlike many home grinders, the KM5 uses a press-and-hold switch. To grind, you keep your finger on the button. Let go, and the grinder stops.
For some people, that is probably fine. For others, it is one of those small design choices that becomes more annoying the longer you live with it, especially if you single dose, weigh beans ahead of time, or want both hands free while the grinder is running.
I first noticed the issue while going through reviews of the KM5. Alternative Brewing mentions the switch in their review around the 3-minute mark. Coffee Kev brings up the workflow around the 2:50 mark and notes that 60 g at setting 3 took roughly 30 seconds. Coffeehaus calls out the switch directly around 8:15, describing it as something that could even be a deal breaker for some people.
Different reviewers framed it in slightly different ways, but the theme was the same: the grinder itself was good, but holding the switch down felt like a strange and slightly awkward design choice.
That was enough for me to get curious.
At the time, I was actually using a Eureka Mignon Crono, which is basically a mechanically identical cousin to the KM5. But after starting MoccaWorks and spending more time around Moccamaster products, the KM5 switch problem felt like exactly the type of thing I wanted to solve: small, mechanical, annoying, and very specific.
So I went on eBay, found the cheapest KM5 I could, and ordered it.
The problem was simple. The geometry was not.
The basic idea was obvious from the beginning: create a small hands-free accessory that lets the KM5 run without having to physically hold the button down.
But I did not want to solve that by modifying the grinder.
No wiring.
No disassembly.
No adhesive.
No permanent changes.
The whole point of MoccaWorks is to make accessories that respect the original machine. They should feel like useful additions, not hacks.
From the start, I knew I wanted the part to mount using the two front feet of the grinder. The KM5 already has two front legs, and those gave me a clean mechanical reference point. The Grind Toggle slips over those front feet using two matching holes in the accessory body, anchoring it in position without needing tape, screws, or clips around the housing.
That part of the concept stayed consistent.
What took more work was everything around the switch.
Prototype 1: close, but not close enough
The first prototype was mostly about proving the mounting concept.
I measured the grinder with calipers, modeled the basic geometry, printed the part, and expected it to land pretty close to where it needed to be.
It did not.
Despite taking what felt like a ridiculous number of measurements, the first version simply was not close enough to the button to activate it properly. That is one of the funny things about designing around an existing product: you can measure all day, but until the part is actually sitting on the machine, you do not really know how all the tolerances stack up.
The first version confirmed that the mounting idea worked, but it also made it clear that the pivot point and switch interface needed more tuning.
Prototype 2: better fit, better feel
The second prototype moved closer to the actual functional design.
At this stage, the main challenge was not just “can it press the button?” It was “can it press the button in a way that feels smooth, repeatable, and not sketchy?”
That mattered because the KM5 switch was never designed to be held by an external accessory. If the toggle pressed too aggressively, it felt wrong. If it barely engaged, it became unreliable. If the pivot geometry was off, the action felt clumsy.
The goal was to make the switch engage gradually as the toggle rotated, instead of suddenly loading the button all at once.
That led to the current design direction: a varying-radius geometry that slowly engages the KM5’s on switch as you rotate the toggle. In plain English, the contact surface changes as it moves, so the pressure ramps in more smoothly rather than just jamming into the button.
It is a tiny detail, but it is the difference between something that technically works and something that feels like it belongs there.
Prototype 3: simplifying the part
The third prototype was about tightening everything up and integrating in that radial design.
By that point, the core geometry worked. The remaining work was about manufacturing, fit, and reliability.
I refined the activation feel, cleaned up the body, and started thinking more seriously about how the part would actually be printed in small batches. One of the less glamorous but important improvements was integrating removable support structures directly into the underside of the design. That made the part more efficient to manufacture while keeping the final shape clean.
There was also a real-world tolerance issue along the way. One prototype unit snapped on first use for a customer, which is exactly the kind of thing you only find once parts leave your own desk and start getting used by other people. That led to another round of tolerance updates and small geometry changes.
The current design is the result of those fixes.
What the final Grind Toggle does
The final Grind Toggle is a small matte black PLA accessory for the Moccamaster KM5 grinder.
It slips onto the two front feet of the grinder and sits in front of the switch. To use it, rotate the toggle into position and it gently holds the KM5’s front button down. Rotate it back, and the switch releases.
That turns the KM5 from a press-and-hold grinder into a hands-free grinder, without changing the machine itself.
It is especially useful if you:
- single dose your beans
- weigh beans before grinding
- grind larger batches
- want to use both hands while the grinder is running
- find the stock KM5 switch slightly annoying or time-consuming
It does not add electronics, timers, batteries, or complexity. It just solves the one workflow issue that kept showing up in KM5 reviews.
Why this is a very MoccaWorks product
This is exactly the kind of product I started MoccaWorks to make.
The Grind Toggle is not a reinvention of the KM5. It is not trying to turn the grinder into something else. It is a small mechanical fix for a specific daily annoyance.
That is also why 3D printing makes sense here. This is a niche accessory for a specific grinder, with geometry that needs to fit around a real object and evolve through testing. It is the kind of product that probably does not make sense for a large manufacturer to tool up, but makes perfect sense as a small-batch accessory.
A tiny problem, solved properly.
Available now
The Grind Toggle for Moccamaster KM5 is available now from MoccaWorks for $28 USD.
It is designed specifically for the Moccamaster KM5 grinder and is intended for anyone who wants a cleaner, hands-free grinding workflow without modifying their machine.
The grinder is (obviously) not included