I took apart a retired burr-type coffee grinder and had a hard time because I couldn't figure out how to take it apart nondestructively. After everything was taken apart, I still was puzzled. While I thought over that problem, I took a closer look at the grinding burrs salvaged from the machine.

I had expected the static burr to be different from the rotating burr, but they appear to be identical parts. Once cleaned up, the only difference was damage visible on the rotating burr. It had been held by rivets that I drilled out and the drill bit scraped off some material. I suppose any optimization for better static vs. rotor performance wouldn't have been worth the cost of having a different part to manufacturer.

They show minor wear after a few years of use, not nearly as much as I had expected. This material is quite tough standing up to the abuse of grinding coffee beans, far beyond what I can reasonably expect to 3D print. However, I am confident I could design and 3D print some other mechanism to reuse these grinding wheels. I'll put them in the bin of interesting salvaged parts.

Back to the mystery of the grinder motor: while putting the motor away with other salvaged motors, I noticed strong similarity between the burr grinder motor (right) and the Bodnum chopper grinder motor (left). Their bodies have slightly different diameters and lengths, but show very similar construction techniques. The output shaft and mounting also look very similar.

Once I removed the mounting hardware, the two motors output ends are nearly identical. The only difference I can see is the Bodum motor (left) has a slightly longer threaded length.

With that interesting comparison, I turned both motors around. The motor shaft on the left had a slot so I can use a flat-blade screwdriver to keep the shaft from turning while I unscrew the chopping blade. There was no such visible slot on the right side motor, and that contributed to how my teardown became destructive. For the left side motor, I kept the two screws that mounted the motor to the base. The right side motor had two similar looking screws in identical positions. When I was going around removing every fastener I can find, I somehow overlooked this pair.

Removing all the tail end hardware showed an equally close resemblance between the two motors. While there is no flat slot for a screwdriver, the exposed shaft does have slightly flattened sides so I could grab them with an adjustable wrench. This would have allowed me to keep the motor shaft from rotating as I unscrewed the grinding burr and, from there, take the burr grinder apart nondestructively. This would have been good to find out earlier, now it is too late for the dismembered grinder. I'll try to keep this lesson in mind for future teardowns.