Posted Mon May 9, 2011, 8:03am Subject: Re: Hario Mini Mill Slim
Netphilosopher Said:
...12 clicks is between 250-350 particles per bean, but the grind size is very inconsistent. Large chunks with pieces that are easily 1/4 the size next to it, and a bit of finer particles.
Simply put, I divide up a sample grind into small samples, and with surgical loupe I do actually count approximate particles on a white piece of paper. I don't count shreds of chaff. If a particle is WAY smaller, I count it as "dust".
I'll try it several times, and check a couple of sample grinds. To make it easiest, I'll divide up piles to get the count down to about 50-100 particles. I started out grinding two beans, but found consistent enough results to just grind one bean and try it a couple of times.
For example, on 12 clicks, I'll grind one bean, then divide the resulting pile in half twice (1/4). I'll count the particles in one and sometimes two samples - It'll be usually repeatable within 20 or so particles.
My last try at this had two of the eight piles of grounds that counted to about 68 particles in one pile and about 82 particles in the other, with the remaining 2-5% of the sample what I would characterize as "dust".
On 8 clicks, I divided the pile in half 3 times (1/8) and had particle counts approximately 150 give or take for two samples, but this took a while so I recombined the pile and divided it into sixteenths and checked three samples of these sixteenths - with particle counts around 65-80 give or take - or single bean grind of approximately 1200. Not rocket science, not a perfect measurement system, but it works and is repeatable enough for me.
On setting 10, I get about 100 fairly evenly sized particles if the sample is divided into eighths. That's about 800 particles per bean - or on par with the finer side of drip or bordering on flavor cup type grind. Visually comparing them to samples it is obvious this is finer than typical Maxwell House drip, and approaching appearance of Keurig cups or Flavia (both of which I have access to).
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
pioneer478 Senior Member Joined: 6 Aug 2007 Posts: 78 Location: MD Expertise: I love coffee
Grinder: Baratza Vario Drip: Technivorm KBT741, Chemex Roaster: Behmor
Posted Mon May 9, 2011, 2:26pm Subject: Re: Hario Mini Mill Slim
Well done..no one can ever accuse you of not being detailed enough in your analysis! :)
I'm currently using the Mini Slim with an auto drip brewer at work, and so far 8 clicks seems to be my preference. However, I have to admit - I'm a bit disappointed at the overall consistency of the grinder. Yes, you can expect more variance in particle size the coarser you get, but even at 8 clicks, I notice what I consider to be a decent amount of "rocks and boulders" in the mix. Maybe I'm being overly harsh since I use a Vario at home, but I swear my grind is noticeably less consistent than my Infinity was (which admittedly is a great entry-level burr grinder, but I'd still expect more from the Hario).
Oh well, for work it'll have to do - if I had more room I'd just bring in the old Capresso..but unfortunately my cramped cubicle isn't getting any bigger. :\
Posted Tue May 10, 2011, 4:33am Subject: Re: Hario Mini Mill Slim
This method of determining grind size is also cheaper than a set of sieves to size and statistically analyze particle distribution.
I had a friend years ago (lost touch with) who was working on what he called a home "coffee bean extruder/breaker" for more consistent "grinding" of larger grind sizes. This is before I learned a lot about coffee, and before the internet was ubiquitous, so back then I didn't understand why this was important.
The basic concept used a series of small drums that were geared together, turning the crank would "break" the bean into progressively smaller chunks - you just removed or added the last three or four of the extruder drums to get the desired size.
I have no idea if it ever worked, but I can see the usefulness - controlled "breaking" of the bean rather than twisting and grinding it, less dust, more consistent particle size (since small particles would drop through the drum and get to the bottom to be appropriately "broken" to the correct size, rather than spend time in the burrs getting progressively ground along with your desired particles).
Interesting, anyways.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Mon May 16, 2011, 5:19am Subject: Re: Hario Mini Mill Slim
And I discovered something this weekend.
I noticed the inconsistent size and watched the grinding on setting 12. The inner cone of the grinder was visibly eccentric with just a little bit of sideload. You could almost see the large grind chunks pop out of the large clearance area and the powder come out of the tight side.
After staring at it a bit, moving parts, and then full disassembly, I noticed a few things.
-During operation, the central drive shaft has a significant amount of slop. I could wiggle the shaft and watch the center cone move around.
Upon disassembly: -there are two bushing/bearings on either end of the central drive shaft. These are not very tight to the shaft, but are definitely intended to hold the shaft in place during grinding. -The center cone has a locked key plastic insert, but the ceramic center cone can move around a bit. -The outer part of the ceramic grinding surface is keyed to the housing, but also has some slop. It is locked in place when the receiver is attached.
The top has a very good fit to the center shaft sleeve, it is obviously intended to support the crank end of the sleeve during grinding.
I went to the two bushing/bearings on the shaft, marked where they were, then added tape around the shaft to make this a very tight fit on both ends.
Upon reassembly, the center shaft was VERY stable. Surprisingly, still very little resistance, even though the bushing/bearings were fairly tight.
I set the grinder to 12 clicks, then pushed the cone back several times to "center" the outer part of the burr, then careful not to disturb the outer part, screwed on the receiver.
Ground 15 grams of beans for coffee - the grounds were remarkably consistent, with probably 60% less dust. The puck usually comes out after brewing in two parts (brewing inverted Aeropress) - the "boulders" settle against the plunger, the dust ends up against the filter. Previous to these mods, the puck would be about 1/4 "fine packed sludge" against the filter and boulders against the plunger, and would frequently come out of the Aeropress in a dual layer puck.
Now, the puck ends up with a very small layer of sludge fines on the filter, probably less than 2mm thick, then the remaining puck is made up of classic Press Pot grounds. Consistency under magnification is awesome.
Note that this requires removing the central shaft - this is not typically part of disassembly.
(Click for larger image)
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
austin Senior Member Joined: 23 Apr 2011 Posts: 19 Location: Los Angeles Expertise: I like coffee
Posted Mon May 16, 2011, 10:52am Subject: Re: Hario Mini Mill Slim
@NetPhilosopher-
I tried cleaning up the slop in the mini mill using your mod ideas with the tape at the two bushings. It cleaned up the shaft wobble considerably. However, I went a step further and wound tape around the outer ceramic burr so it would fit tightly in the plastic housing. Before that, the outer burr would wobble as well in the plastic sub assembly.
There still is a little bit of grind wobble that I believe is caused from the slop between the inner cone and the shaft. My next step is to add tape where the inner ceramic cone's bushing meets the shaft.
Posted Mon May 16, 2011, 1:28pm Subject: Re: Hario Mini Mill Slim
@austin,
Those were my next steps, too. I think the housing is well centered to the shaft sleeve, so tape-wedging the outer burr should be well centered.
I think you'll have to do a couple things to the inner cone: -decrease the slop of the plastic insert to the shaft (without interfering with the spring doing its job), and -decrease the slop of the inner cone burr to the plastic insert.
Soak the center cone burr in warm water for about 5 minutes - the way the center piece of plastic gets softer tells me it's probably nylon. Just pinch the plastic and push it through and it pops right out without breaking.
Hopefully, once the slop is removed, it won't interfere with the spring and how it pushes the center cone out to the screw to set the grind distance between the burrs - that was my initial concern and why I didn't do it at first.
The first mod was so dramatic in the grind consistency I got all geeked up and had to make coffee right away. LOL
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
austin Senior Member Joined: 23 Apr 2011 Posts: 19 Location: Los Angeles Expertise: I like coffee
Posted Mon May 16, 2011, 2:29pm Subject: Re: Hario Mini Mill Slim
I took care of the slop in the inner cone burr to the plastic insert by wedging in two fold post-it notes in between the circular plastic insert and the fat side of the inner cone. I then traced the circumference of the cone on the post it notes, pulled them out, cut them and wedged them back in. Not sure if that is a clear explanation, but just wedge/shim something in between the plastic insert and the bottom of the cone and you'll see that it prevents the plastic from moving inside the ceramic burr.
Now all I have to do is clean up the slop between the shaft and the plastic insert.....
Posted Wed May 18, 2011, 7:57am Subject: Re: Hario Mini Mill Slim
Got rid of the last of the slop on the inner cone. It's just a touch sticky, and I stretched my inner cone spring to provide some more force.
Consistency is vastly improved. However, it grinds smaller now, I had to go back and adjust grind settings.
Dust is absolutely MINIMAL on even large grinds. Wonderful.
I now grind just about press pot at 16 clicks, drip at 11 clicks, and low-contact time Aeropress at 9-10 clicks. VERY consistent grind. At 8-9 clicks, the result is indistinguishable from Keruig K-Cup grounds under magnification.
Operation is also much smoother, markedly reduced "jerkiness" and just a consistent sound during grinding. At press pot setting, all of the huge boulders are gone, and the dust is pretty much as minimal as I have seen with a Ditting. I'll probably go get some coffee ground to press pot in a Ditting just to get one more comparison, but it makes a good 2+minute contact time coffee.
Now, to find a 5-point socket so I can use an electric driver... ;-)
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
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