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I have a Bodum Bistro grinder that I bought used a couple of months ago, and have been fairly impressed with. It started making a horrible gear-grinding noise today, after getting a very small, very hard bean stuck in the burrs. Being physiologically incapable of doing otherwise, I tore it down to see what had happened.

I was shocked to see that the (delrin? nylon?) gears actually aren't all chewed up at all. They were just choked with dirty, messy, nasty, oily grinds, presumably keeping the motor shaft from engaging properly. I ran the gearbox through the dishwasher to clean it all out, and I think there's hope that this thing will work again when I put it back together.

But I just had a horrible thought: The gearbox isn't sealed. Maybe the mess in the gearbox was a combination of grinds and grease.

Thoughts please: should I be packing the gears with silicon grease before I put it all back together?

Update: What I did

I used white lithium grease, after applying foil tape to seal openings between the coffee area and the gearbox area, figuring that there would be a very low likelihood of the grease aerosolizing and getting into the coffee area.

Reassembly was a bear, though. I ended up hardwiring past the rocker switch.

2.5 Years Later:

It's been 2.5 years, and I have not tasted the grease, and the grinder is still running strong.

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Yes, I assume the gearbox was originally lubricated to function properly somehow. I cannot believe the gears just rotate by their own.

And about the sealing. Such devices produced in bulk mostly do not care about proper sealing, no worries. Therefore, some parts may get in contact with your food.

Finally, about greasing... There are food-safe lubricants made out of vegetable oils for food machinery. These are generally aroma-free, so they won't affect the taste of your coffee. You can buy one of them and use. I don't link as you can easily search the net.

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  • Yes, there is food-grade silicon grease available. But Delrin has very high lubricity, and does not require grease in low torque applications; it is not a given that the gearbox was pre-lubricated. The concern is that greasing a non-sealed gearbox will choke the gear teeth with a dense mixture of grounds and grease. If this happens, the gears will not fully engage, and will wear prematurely.
    – Autumn
    Commented May 6, 2018 at 19:28
  • @DS Justice Couldn't you examine whether what you've found was the remainings of a lubricant or of the coffee itself?
    – MTSan
    Commented May 6, 2018 at 20:06
  • No, I quite stupidly put it in the dishwasher before thinking about it. I thought I was just seeing disgustingly oily dark-roast grinds from the previous owner. It was only in retrospect that I realized that it might have been mixed with grease. In any case, this morning's project was to grease and seal the gearbox. We'll see how it goes.
    – Autumn
    Commented May 6, 2018 at 21:07
  • @DS Justice I see. You know, the coffee grounds are quite greasy by themselves. Hard to distinguish. After all, please write back the results.
    – MTSan
    Commented May 7, 2018 at 6:55

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