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Shop-built Electric Coffee Grinder

January 7, 2020

Engineers love coffee, without it society as we know it would likely cease to function. So of course our design studio has the obligatory diner style coffee maker that spurts out gallons of murky warm “coffee” that’s somehow both overwhelmingly bitter and completely tasteless. That’s not to say ineffective, that same coffee maker likely fueled decades of amazing products from the infamous Osborne computer, Neo’s glasses in the Matrix, through to modern joys like the Hatch-Baby series of products. However some of the more discerning engineers such as myself have grown accustomed to the great advances in the world of coffee has seen since the diner behemoth was incepted, so I keep an electric kettle and Chemex brewer at my desk to make my daily brew. Coffee grinder engineering was not the field I thought I would find myself in. Well, here I am…

 Like a lot of coffee enthusiasts I also like to grind the beans right before brewing to ensure the best flavor, and for years I’ve used a little Porlex hand grinder which has served me well. Recently however I’ve found myself making multiple pots everyday as more converts around Studiored peak their head over the cube wall to ask for a cup, and the time spent hand grinding each batch was getting excessive. Any sane person would simply buy an electric grinder and be done with it, but I’m not a sane person, I’m an engineer with a problem and an entire building full of materials and tools to solve it.

So one evening after work I headed out to the workshop to execute the needlessly elaborate idea in my head. I wanted to use my favorite materials and parts from some of my favorite suppliers in an absurd but effective electric conversion for my simple manual grinder.

The first problem was how to couple the drive from a gear motor to the shaft on the grinder, at first blush it looks like a simple hex shaft that could be driven with any manner of OTS hex drivers, however the engineers at Porlex clearly wanted to stop caffeine crazed lunatics with drills from chucking their grinder up and spinning it until the plastic internals melt, so they made the shaft a pentagon rather than a hexagon. I however am not a caffeine crazed lunatic with a drill, I’m a caffeine crazed lunatic with a lathe and a file, so after drilling the requisite shaft bore and pilot holes I filed in a pentagonal hole, proving that no matter how idiot proof something is there will always be a better idiot.

The rest was simple enough, I used some IGUS track and aluminum tubing to align the gear motor with the grinder (which is secured with a single PEM thumb screw for easy removal), a gas spring to hold the motor up out of the way while filling the hopper, and a nice big stainless button to turn it on and off. The 100RPM gear motor is roughly equivalent to human grinding speed so I’m not worried about melting anything and has more than enough torque for any grind/bean combination. It’s not quiet by any stretch of the imagination but I think that should be considered a feature since the deep rumble lets everyone in a 100ft radius know another tasty batch is on the way. Stay tuned for the next episode of Coffee Grinder Engineering!

Check out the video below to see it in action.

Or check out more of George’s hacks Here.