Into the gearbox of the Weber Key

Grinders are one of the keys to exceptional espresso. Discuss them here.
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#1: Post by danetrainer »

I delved into my Key as it's had a month of break in and I was getting a large "clack" when I dropped the beans in, and I also wanted to add some Super Lube to the gear drive.

I first very closely inspected the alignment and it is exceptional, one slight issue is if I pushed on the bottom of the burr the entire shaft floated up and down a small amount, about .010". You would want to inspect that with the burrs set to a more coarse setting so I just turned it 1 full turn more.

Also, there was a large amount of "backlash" for the gears (approximately twice what would be proper) so I addressed both of those items. I've adjusted plenty of differential gears during my profession and the spiral bevel gearset in the Key is of course much simpler.

First I wanted to address the up & down movement of the shaft, in the state of grinding beans this really makes no improvement as the force will keep the shaft pushed down. In keeping the gear backlash in a proper range this adjustment helps when it runs free and then the beans are loaded to lessen or eliminate the "clack" sound.

In the first picture I loosened the 2 set screws of the upper collar and pushed it all the way upward and tightened the set screws. This takes an 1/16" hex key.
The lower split ring collar is against the shoulder of the shaft so it can't take up any of the clearance to the lower bearing, there is a thrust washer that sets that.

In the second picture I loosened the 2.5mm set screws on the gear and moved it up to give about .008" backlash. In the "old days" before we had a dial indicator setup to accurately check backlash we had a saying that the movement back and forth was about the thickness of a match book cover.

Finally I just added some Super Lube to the teeth of the gears and installed the cover and it sounds much improved, but all-in-all it actually checked out quite good.
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