Coffee Crusher

Domestic coffee grinders come in two basic sub types, blade and burr. The burr type grinders are supposed to supply a consistent coffee particle size, but they don't. They do a good job of supplying a consistent upper limit on particle size, but they also create smaller, powdered coffee that gums up my grinder and needs cleaning every now and then.

Part of the problem with these grinders is they seem to run on small motors that rely on speed, you can hear the grinder slow down/speed up as more/less beans drop into the blades. This is both inconsistent, because some beans are ground more slowly, and others smashed hard because the blades have chance to spin up to a higher speed. It's also very noisy for a piece of equipment frequently used 1st thing in the morning. Burr grinders also dull over time, making them less good and more noisy.

So, no blades, no high speed motors. We will start with a massively over-spec motor that makes a reassuring quiet hum when turned on. Like a lathe. Through reduction gears, this motor will drive two smooth rollers. These should be quite large diameter, 6" or so, so that the angle is gentle, stopping the beans just bouncing up off the smooth surface.

We feed in beans, they are crushed quietly and efficiently to a size specified by the gap width between the rotors. There should be a hand guard because of the aforementioned over spec motor.