This is a long time coming, but knowing my ability to properly perform searches perhaps it has already been asked many times...

Why the **** are there so many open gaps and creases in a grinder?  It's just begging to have stale coffee pile up inside.  For example, in a Mazzer, why is there a 1-2 mm gap where the burrs connect to the burr carrier?  Inside of the upper carrier, why is there hollowed out space that can hold FIVE GRAMS of coffee?  Why don't the burrs sit flush against the burr carriers?  I'm probably not even referring to the parts properly, I'll explain what parts I'm speaking about if necessary...

GAAAH!  Why the hell do these areas that see SO MUCH coffee move over them have so much room for coffee to hide and stale?  You can clean your grinders every day (hell once an hour) and there is still going to be a ton of coffee that piles up in there.

Frustrations from someone that cleaned grinders today and managed to amass 19 grams of coffee out of the collars of 2 Majors and 3 Super Jolly's...

But this is actually meant to be a question:
-Is there actually a reason (functionally) that these gaps have to exist?  Or are the R+D departments just getting paid too much.

-bry


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Bry,

Im not convinced thats a real substantial amount of coffee for FIVE commercial grinders. In a commercial enviroment like they were designed to be in, accumalation is nearly a non-issue with a good barista like you who actually cares about cleaning it out on a regular basis. Look at it this way, at least the Mazzer is designed well enough that it is easy to dis-assemble and clean easily and at least it's not a large conical(think robur/k10) which holds MUCH more gounds in the chamber.

I just got a new K30 for my home lol, so maybe its not fair for me to comment lol;) anyways, props for keeping your grinder clean. I know what you mean about douching out a Mazzer after heavy use. Take pride in it brotha!


Cheers
Jackson
we had a conversation very similar with compak when the k10 doserless came out. We were getting dose variance up to 2 or 3 grams due to buildup up ever half dozen shots or so. When we talked to the tech department, we found that , at least from their perspective, it was a necessary evil to follow etl and ul approval guidelines. However, i think the robur e only house about a gram extra.
James Hoffmann has a recent post about grinder design on his blog. It's odd that grinders haven't changed all that much during the last fifty years.
they're the platter hard drives of the espresso world
This is really good question, Bry. If you go to Expo this year, perhaps it would be worthwhile to spend some time in the booths asking.

To Chris's observation about UL requirements... the requirement is that it must be impossible for you to cut your finger off with the grinder in its as-shipped condition. In fact, here's the device that is used by the inspector to verify this:

This is the reason that they all ship with those obnoxious doser guards, hopper screws, hopper guards, etc. I think that speaks more to the chute geometry than to the cavities that Bryan is referring to.

The only thing that I can think of to explain these gaps is overly-generous tolerances to facilitate manufacturing. Remember that these companies make tons of these grinders, and that in many cases small gaps are not nearly as big of an issue as the cost of the grinder. That doesn't explain everything, but is certainly relevant in some cases.
I simply say it's the nature of the beast. Fine coffee grounds such as those used for spro are going to find the smallest area to build up in. In a busy commercial setting I see no problems with a bit of retention because it gets flushed out often. Of course it will lead to waste at the end of the day when the grinder is cleaned thoroughly, but what can you do? It is what it is... Later!
You know, it is possible that the gap under the burrs is intentional to allow them to flex a little during use. Just thinking about that a bit, and I suppose it's feasible. Its always tough to figure out what engineering departments were thinking...
If there were no gaps, then the metal would be grinding together. Otherwise you would need lube. Which would create coffee/lube sludge. The small gaps fill so quickly (clean one out, use it once, then take it apart again, you'll see what I mean) they're basically plugging themselves up almost immediately. 19g of waste from 5 grinders is pretty slim.
Bry's not talking about grinds in the feed chute path, or under sweep veins etc. All these can be dealt with via mods and flushes during regular usage. He's talking about grinds that accumulate between the flat under surface of the burrs and the burr carrier they are screwed on. If you remove the burr and look at the lower burr carrier, why are there chambers which simply beg to accumlate grinds and stale rather than a flat surface for the burr to mount on? Is there an actual purpose to those grinds accumulating chambers other than using less metal during manufacturing the burr carrier?

It's not an issue of waste but rather stale grinds accumulating in hidden areas that can only be dealt with by disassemby. Minute rice or Grindz do nothing for this issue.

Jackson Ball said:
Bry,

Im not convinced thats a real substantial amount of coffee for FIVE commercial grinders. In a commercial enviroment like they were designed to be in, accumalation is nearly a non-issue with a good barista like you who actually cares about cleaning it out on a regular basis. Look at it this way, at least the Mazzer is designed well enough that it is easy to dis-assemble and clean easily and at least it's not a large conical(think robur/k10) which holds MUCH more gounds in the chamber.

I just got a new K30 for my home lol, so maybe its not fair for me to comment lol;) anyways, props for keeping your grinder clean. I know what you mean about douching out a Mazzer after heavy use. Take pride in it brotha!


Cheers
Jackson
Think of it this way: at least we're all cleaning our grinders...

In a shop where I used to work, the grinders were never cleaned; to my knowledge, the dosers were never even brushed out.

(pulls blanket back over head in embarrassment).
I have thought of the same question. I've taken the grind platter/burr assembly parts apart literally hundreds of times on many types of grinders and the situation is always the same. There is always this oily paste under the spinning burr and this hard clay-like substance under the platter. Both are quite difficult to remove.

As for the reasons I have to think it's along Brady's line of thinking. Manufacturing tolerances. And possibly heat dissepation. In order to make metal surfaces mate flat against each other it takes special machining. This kind of machining is time consuming and expensive. Most of the spinning platters start their life as a casting and are then finished on a mill. If the piece can be finished in one operation it keeps the price down. The only exception to this I've seen are the big Mahlkonig and Ditting grinders. Espessially the Mahlkonigs. When everything is put together the tolerances are exceptionally tight and there is very little room for the coffee build up. The burrs sit flat against the platter and when you turn the unit on with the top off it looks like it's not even moving. It's actually kind of cool.

As for heat disipation you've got two ways to go. More mass or less. With the Majors and SJ's (or with any other brand for that matter) the burrs are pretty small and the total amount of mass availible for heat transfer and dissipation is limited. Since the burrs are where the heat is generated if they have less mass they will heat up faster but also cool down faster. If the burrs mated flat to the burr carrier in an espresso grinder the whole thing would hold heat longer. Heat distorts metal and brings out the oils in coffee. Also the metals used in espresso grinders tend to be dissimilar. A brass spinning platter with steel (or titanium or ceramic) burrs. These materials all behave differently with heat. If you decrease the surface area between the dissimilar materials you will allow them to act more independantly. When the brass starts to heat up and distort it will not transfer that same distortion to the harder and more brittle steel burr. I think that is why there is space between the two. The same would go for the space between the spinning platter and the floor of the grind chamber.

With the big grinders like a Ditting or Mahlkonig the opposite approch is used. The burrs are massive and are flat mated to a massive spinning platter which is attached to the massive spinning motor rotor via a massive flush fit cone shaped spindle. I think the idea is that when heat is generated by the grinding it is transfered into this giant mass for disipation. Most of the time the heat generated is minimal in comparison to the mass availible and everything is fine. But if you are trying to grind a couple of five pound bags through a dirty grind chamber the heat build up is more than the mass of the grinder can absorb and then the thermal breaker pops.

The other thing I've noticed is that the difference between the compostion of the newly ground coffee and the wierd paste/clay that builds up under the burr and the platter keeps the two from interacting vey much. There is no doubt that if you made a shot with the crap you collected from the undersides of those burrs and platters that it would make you hurl. I just don't think you're going to get much of that crap in your grind durring normal use. It might be that your grinder is not broken in properly until those area are filled in. Who knows?
Mike Sabol said:
I have thought of the same question. I've taken the grind platter/burr assembly parts apart literally hundreds of times on many types of grinders and the situation is always the same. There is always this oily paste under the spinning burr and this hard clay-like substance under the platter. Both are quite difficult to remove.

As for the reasons I have to think it's along Brady's line of thinking. Manufacturing tolerances. And possibly heat dissepation. In order to make metal surfaces mate flat against each other it takes special machining. This kind of machining is time consuming and expensive. Most of the spinning platters start their life as a casting and are then finished on a mill. If the piece can be finished in one operation it keeps the price down. The only exception to this I've seen are the big Mahlkonig and Ditting grinders. Espessially the Mahlkonigs. When everything is put together the tolerances are exceptionally tight and there is very little room for the coffee build up. The burrs sit flat against the platter and when you turn the unit on with the top off it looks like it's not even moving. It's actually kind of cool.

As for heat disipation you've got two ways to go. More mass or less. With the Majors and SJ's (or with any other brand for that matter) the burrs are pretty small and the total amount of mass availible for heat transfer and dissipation is limited. Since the burrs are where the heat is generated if they have less mass they will heat up faster but also cool down faster. If the burrs mated flat to the burr carrier in an espresso grinder the whole thing would hold heat longer. Heat distorts metal and brings out the oils in coffee. Also the metals used in espresso grinders tend to be dissimilar. A brass spinning platter with steel (or titanium or ceramic) burrs. These materials all behave differently with heat. If you decrease the surface area between the dissimilar materials you will allow them to act more independantly. When the brass starts to heat up and distort it will not transfer that same distortion to the harder and more brittle steel burr. I think that is why there is space between the two. The same would go for the space between the spinning platter and the floor of the grind chamber.

With the big grinders like a Ditting or Mahlkonig the opposite approch is used. The burrs are massive and are flat mated to a massive spinning platter which is attached to the massive spinning motor rotor via a massive flush fit cone shaped spindle. I think the idea is that when heat is generated by the grinding it is transfered into this giant mass for disipation. Most of the time the heat generated is minimal in comparison to the mass availible and everything is fine. But if you are trying to grind a couple of five pound bags through a dirty grind chamber the heat build up is more than the mass of the grinder can absorb and then the thermal breaker pops.

The other thing I've noticed is that the difference between the compostion of the newly ground coffee and the wierd paste/clay that builds up under the burr and the platter keeps the two from interacting vey much. There is no doubt that if you made a shot with the crap you collected from the undersides of those burrs and platters that it would make you hurl. I just don't think you're going to get much of that crap in your grind durring normal use. It might be that your grinder is not broken in properly until those area are filled in. Who knows?

Thanks for this really thought out reply. I'm going to sit down and pick it apart when I'm not on bar (shh, don't tell Mike, haha).

Brady, I wish I was going to SCAA this year, but it's just not possible with the launch of the new roastery cafe and trying to expand the wholesale operations, etc etc. I have thought about sending an email to...?... Mazzer? about why these are designed the way they are. Even if it took 1 month for them to get back to me, at least I would know for sure, right?

Matt, I've read that article. It's actually what got me (re)thinking about this all over again. I wrote a similar blog post about a month before his popped up just begging why we haven't seen more advancements on the grinder front, then my thoughts trailed off... then his post came up and got me thinking again... and then I cleaned the grinders and lost it, haha.

Mike is spot on, I'm not talking about what's in the "throat" or what's under the veins in a doser, I'm talking about that clay-like crap that builds up under burrs and in "burr holders" as Cafe Parts likes to call them, or "upper cutting holder" as the manual on Espresso Parts calls them. Indeed some of the coffee is really fine particles but some of it is so large that I wouldn't even brew a press with it... things that look like quartered beans.

Manufacturing tolerances seems like the most likely cause to me, that being said, wouldn't you pay $500 more for less tolerances? Or would we be talking huge amounts more (like add a zero kind of amounts). I mean, the Speedster is one of the most lusted after machines out there right now, and Kees' attention to manufacturing detail is one of the things that makes them so appealing. There aren't any manufacturing tolerances on those things (well, not really...). Even then, it's also one of the most expensive machines on the market, yet there is a 2+ year waiting list.

Is it just that there are so few people that care about grinders that a "groundbreaking zero-tolerance" grinder wouldn't make a splash, 'cuz I sure as hell think it would make a huge splash.

BTW, the 19 grams wasn't including what was in the "throat," "column," or attached to the burrs, just what was under the burrs, I misspoke a little bit earlier (or wasn't clear enough... whatever).

Visualize with me a minute... the main area I'm talking about is:
- close your hopper "gate"
- remove the hopper
- remove the beans that were under the "hopper gate" from the "upper burr holder"
- unscrew the adjustment ring
- the next metal piece is what I have been referring to as the "upper burr holder." The part that is sitting on the springs.
- look down inside the "collar" where the beans feed from the hopper into the grinding chamber/burr area/whatever...
.... RIGHT THERE! (*points at the gap in visual picture* lol) between the part that is sitting on the springs and the actual burr itself, on the inside where the beans feed down into the middle section... WTF IS THAT, MAN! That's like 2 mm! That's a hell of a large coffee particle! Tolerances...psh... F that, man! That's horse**** slacking off right there. We need to go be pains in the arses of some people I think. :0)

... unless of coarse it does serve some purpose and isn't just "tolerance."

Thanks for the responses guys.

-bry

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