How important is grinder's alignment? Is good enough good enough?

Grinders are one of the keys to exceptional espresso. Discuss them here.
samuellaw178
Team HB

#1: Post by samuellaw178 » Mar 11, 2016, 6:00 pm

In order continue the discussion in good spirit and not driving the thread off topic, here's the topic I'm particularly intrested in:
No coffee grinder that I have ever seen or used is capable of crushing coffee beans with any degree of bean to bean precision regardless of the mechanical precision and alignment of the actual burr and mounting.
What manufacturing tolerances have to do with what's discussed here? And what do you mean by bean to bean precision?

I'm guessing you've done a full blown comparison of different grinder designs, tested different levels of misalignment, used LPA to test particle distribution and effectively arrived at your conclusion?
I suppose we can agree that a gross misalignment will affect the grind results greatly. These are the types of misalignments that are obvious even to the naked eyes - no indicator dial is needed.

Now here's where it differs : For those who has used a 'perfectly' aligned grinder (for example, either your own custom made or even Frank's Titus grinder) and a slightly less than perfectly aligned grinder, what are the difference/improvement that you've experienced? Taste wise? Static? Distribution?

From my own experience with a limited few grinders, further alignment did not seem to make much of a difference if the alignment is already 'pretty good' in the first place. When I tried being anal and aligned the grinder so that it seems better, I did not notice any significant improvement. Should I expect some miracles to happen once I cross that magic 'perfection' line?

It is in my opinion and as highlighted - the beans cutting process is a pretty imprecise process, the burrs are manufactured with a tolerance (look at the cutting surfaces for instance). Can a perfect alignment improve the precision of an inherently imprecise (within reasons) process? It reminds me of the acedemia scenario - it is so common for a student's math/sciences calculation to quote a precision down to 5 decimal point (because they can) whereas the raw data only has +/- 1 decimal point accuracy. This obviously does not seem to make sense, and seems to be what's happening with the extreme alignment analysis here?

However, it is only my limited opinion derived from my limited experiences. Keen to hear more.

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nickw

#2: Post by nickw » Mar 11, 2016, 6:34 pm

Yes, alignment makes a huge difference! :)

Axial alignment is more important than radial in terms of taste/grind distribution.

How much of a difference it makes depends on the grinder. For example:
- On my Versalab : The difference was huge. From the factory it was .065mm out axially. The first alignment I got it to about .025mm axially, and the second time around .01-.012mm, both through careful assembly. It went from grinding at 45˙ past zero, to about 60˙ to about 90˙. I can go back and pull some of my previous statements on alignment/taste (or you can search my posts), but in a nut shell, it was shocking. Even my friends noticed and asked what I changed (not seeing any visible difference in equipment). It didn't have my refractometer back then, so I can't give any before/after EY measurements.
- On my EK43, aligning made a positive difference, but nowhere as near as big as the Versalab (even though it was out a similar amount). I suspect the deeper .3mm fines channels allow it to be more forgiving. EY went up about 1-2% for espresso, depending on the coffee.

Also note, it's not just alignment, but there is also runout (think of runout like wobble). So alignment is having them run on the same axis, run-out is wobble on that axis.

As to where alignment/runout differences start dropping off?
Previously I would of said around .01mm (10um/micrometer). Which is about 5% of the target 200um size. Apparently around that size, variations in bean structure and brittleness start make a bigger impact. I noticed with my Versalab a big difference between .025mm to .01mm (the size of gains in the cup actually surprised me). Some of Frank's machines are down to the .005mm area (and I think he said after about .01mm you don't really notice anymore). With my EK43 the different between .06-.07mm axial misalignment to current (estimated .015-.02mm) was a noticeable gain, but not as dramatic as the Versalab. So I now am suspecting the differences will vary based on the burrset (type, size, cut, texture, etc). Whether it's become some burrsets are more forgiving, or less resolving is unknown to me.

You also not "cutting" the bean up per say. Burr grinders grind by attrition.

If you would like, I can also share a bunch of video's with you. Such as Christian Klatt of Mahlkonig, or Randy Pope of Bunn.

I could speak ad nauseam about grinders and alignment, so rather than go off, please just ask any questions you have.

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TomC
Team HB

#3: Post by TomC » Mar 11, 2016, 7:22 pm

I think the final frontier for coffee grinders will be much higher precision in crafting the burrs themselves. But few will be able to benefit from this, what good does it do to have even more precise, ideally cut burr patterns if they're mounted to standard grinder motor shafts that still suffer from poor alignment.

I'd still love to see a large blind test done at a major coffee event, where a large group of folks could grade shots pulled from one of these ultra precise grinders versus the common commercially available ones. I believe precision helps, but I think it also gets to a point of diminishing returns.

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canuckcoffeeguy

#4: Post by canuckcoffeeguy » Mar 11, 2016, 8:20 pm

nickw wrote:Yes, alignment makes a huge difference! :)

Axial alignment is more important than radial in terms of taste/grind distribution.
We're seeing alignment discussed more and more recently. Matt Perger has raised the issue, too.

Basically this has me paranoid about my grinders: K10PB, Pharos and Vario. I bought each of them new, none second hand.

How confident can I be in their correct alignment?

Or more broadly speaking, how prevalent is grinder misalignment in the wild?

Are we talking about a global pandemic of misalignment?

I have no expertise in measuring alignment and working with precision tools. I'm even terrified about taking my K10PB apart after reading the horror stories of cross threading and just making things worse by playing Luigi Mazzer at home.

And is this why Mahlkonig's K30 seems to punch above its weight? Perhaps it's supremely aligned with precise tolerances. Giving it great performance relative to others who might have bigger burrs, but are not as well fabricated.

samuellaw178
Team HB

#5: Post by samuellaw178 » Mar 11, 2016, 8:24 pm

nickw wrote: Axial alignment is more important than radial in terms of taste/grind distribution.

Also note, it's not just alignment, but there is also runout (think of runout like wobble). So alignment is having them run on the same axis, run-out is wobble on that axis.

You also not "cutting" the bean up per say. Burr grinders grind by attrition.

I could speak ad nauseam about grinders and alignment, so rather than go off, please just ask any questions you have.
Thanks Nick for highlighting the point on axial alignment.

I had gone through some of the videos before. However I am not aware if they mention anything about the accepted runout tolerance, or how do you consider a grinder perfectly aligned, and what are the benefits of going from good enough tolerance to 'perfect' alignment. I know alignment is important, but I'm not sure how good is good enough thus the OP. On my Pharos, HG-1 & Lido, aligning them had never achieved me anything significant/noticable as compared to the difference between flat burrs vs conical burrs.

On the Versalab, do you do WDT on your shots before the alignment?

I've read often enough that alignment makes a huge impact on Versalab's operation. My impression/guess was two fold - one is due the design and secondly the shaft runout was too much to begin with. On the design front, my impression was the Versalab has a static wiper underneath. If this is out of alignment, I suppose that will affect the distribution and retention(thus low EY). On a perfectly aligned Versalab, if you remove the wiper, does it have static, do you still need to distribute for high EY without channeling?

Also, 'cutting' is just a layman term as I do not know the right jargon. :oops: To my understanding, attrition is an imprecise process. Basically you have beans fracturing and 'exploding' if you will,to all sort of particle sizes. Then you're hoping the size distribution will fall into the right range with the right ratio, and course the burrs gap opening is helping with determining the grind size threshold. None of these seems like a precise process.

samuellaw178
Team HB

#6: Post by samuellaw178 » Mar 11, 2016, 8:34 pm

TomC wrote: I'd still love to see a large blind test done at a major coffee event, where a large group of folks could grade shots pulled from one of these ultra precise grinders versus the common commercially available ones.
Would love to see that too. That will answer the question posed by Ryan above (which I believe the question most of us have in our mind as well)
canuckcoffeeguy wrote:How confident can I be in their correct alignment?

Or more broadly speaking, how prevalent is grinder misalignment in the wild
Based on my personal experience, to achieve a perfectly aligned grinder, too much effort is needed (hours and hours of alignment) and you're still not guaranteed a perfect alignment (too many things can go wrong). When translated into a manufacturing scenario, that is not feasible without a significant increase in production cost. Also, your rejection rate of less-than-perfect grinder will sky rocket. Are the consumers willing to pay for 2-4 times more for an increased in precision which they will hardly notice a difference? (Think of a perfectly aligned HG-1 for 3k or a perfectly aligned Compak K10 for 3k)

Think of this like the VST baskets, even their basket holes aren't perfect - and that is just punching holes on a metal sheet, how hard can that be, right? :P

HoldTheOnions

#7: Post by HoldTheOnions » Mar 11, 2016, 9:11 pm

I did the thing where you clean it out and then note where burrs touch, turn it a little, note where the burrs touch again, etc. The difference between the min and max was about a mm of adjustment. I don't know if that is a little or a lot on ceado, it seemed like a little, so if it's a lot let me continue in ignorant bliss please. :wink: Point being, you could do that, then put a spacer under one side and get further off than where you are, and see if you can taste a difference. If you can't taste any difference, then getting more aligned prolly not make much difference either? Maybe that's flawed in ways I can't cipher.

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nickw

#8: Post by nickw » Mar 11, 2016, 9:35 pm

canuckcoffeeguy wrote:... broadly speaking, how prevalent is grinder misalignment in the wild?

Are we talking about a global pandemic of misalignment?
Most grinders are pretty bad. You have:
- the inherent design (and how good it is)
- you have machining tolerances on the parts
- plus you have assembly tolerances
Final spec is a combination of the three.

Essentially we have mass manufacturing done to a price point. Right now we're getting what we pay for. Building a high spec machine is going to cost more money. I don't blame manufactures currently.

To be honest, most people won't like a high spec grinder at first. The better the alignment the smaller the window will be to get a good flow rate. Too course and you'll have gusher, to fine and it will channel. But within that window, things can taste a lot better!
But right now, we have the opposite: People praise grinders which are more forgiving of grind size and flow rate. Blah!
canuckcoffeeguy wrote:Basically this has me paranoid about my grinders: K10PB, Pharos and Vario. I bought each of them new, none second hand.

How confident can I be in their correct alignment?
Sorry, not trying to make you paranoid. If you're enjoying your coffee and you're happy, then all is well for you :)

If you want to try and check:
You can use the felt marker method. Essentially you open and clean the grinder, then paint the burr edge (fines cutting area) with the marker. Reassemble the grinder, and run it until the burrs touch/zero. Then open an re-inspect. You'll be able to see where they touched, and get a rough idea on axial alignment. Depending on the grinder you can potentially make it better.

To clean the marker after you can use rubbing alcohol. Rubbing alcohol is also really good at cleaning coffee grim and oils too. I use it on a cotton pads (sold for make up removal), it works great.

Also a warning: if you're not comfortable/confident in messing with things, then best to leave it be. You could easily make it much worse.
canuckcoffeeguy wrote:And is this why Mahlkonig's K30 seems to punch above its weight? Perhaps it's supremely aligned with precise tolerances. Giving it great performance relative to others who might have bigger burrs, but are not as well fabricated.
Yes, I think so. Mahlkonig seems to do best out of the large major manufactures.

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Terranova
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#9: Post by Terranova » Mar 11, 2016, 10:18 pm

canuckcoffeeguy wrote: Basically this has me paranoid about my grinders: K10PB, Pharos and Vario. I bought each of them new, none second hand.
How confident can I be in their correct alignment?
Don't get paranoid and enjoy your espresso.
If you weight the output shot by shot and the flow rate, time, weight and last not least taste stays the same, than it is very unlikely that your grinders suck.


canuckcoffeeguy wrote: And is this why Mahlkonig's K30 seems to punch above its weight? Perhaps it's supremely aligned with precise tolerances.
They are "punching above their weight" because burr size is often getting overestimated but at the end the grinders with bigger burrs are mostly better assembled, aligned, so the output can be more consistent just because of less run out, but not just because of the burr size.
Mahlkönig is machining the best burrs (imo) and a grinder can only be as good as the weakest part of it, (alignment) same like the performance of your PC.

So the conclusion is: less run out less boulders, less over-extracting, more consistency. I also had some good shots out of misaligned grinders, it seems that just sometimes it is the right mix out of a certain particle size range, but it is difficult to have consistent and reproducable results.

You can do some little things to have the burrs with low radial play but just radial, the rest are many different numbers from many parts i.e tolerances which meet at the burrs.

Christopher Handon claims that his tested grinders are running parallel within 1 micron. But I think he also believes in fairy tales.

https://twitter.com/chhendon/status/651154278128619521

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nickw

#10: Post by nickw » Mar 11, 2016, 10:31 pm

samuellaw178 wrote:Thanks Nick for highlighting the point on axial alignment.

I had gone through some of the videos before. However I am not aware if they mention anything about the accepted runout tolerance, or how do you consider a grinder perfectly aligned, and what are the benefits of going from good enough tolerance to 'perfect' alignment. I know alignment is important, but I'm not sure how good is good enough thus the OP. On my Pharos, HG-1 & Lido, aligning them had never achieved me anything significant/noticable as compared to the difference between flat burrs vs conical burrs.
You're welcome, I do what I can. I'm still learning like everyone else (I could be wrong on some things too). It's a fun and deep rabbit hole.

Most companies don't state acceptable alignment/runout. Otherwise we could hold them too it.
I've only seen Mazzer and Frank state anything.

Mazzer says they aim for .02mm, which if they actually did hit, would be pretty good (I haven't seen it, but need to test more).
http://sprudge.com/mazzer-factory-tour-44860.html
The whole 0mm tolerance thing isn't true. Everything has tolerance.


Frank says he shoots for .005mm, and everything is below .01mm. I believe him. But look at how much work he goes to:
Heating the bearings to expand, and freezing the shaft (shrinks it) for a press fitting: https://www.instagram.com/p/BBJDNHNLMFJ/
Bench grinding/lapping the outer conics (which the flats sit on): https://www.instagram.com/p/4-anxCrMKx/
Measuring final axial on static burr: https://www.instagram.com/p/4-VMkhrMBD/
Measuring final axial on rotating burr: https://www.instagram.com/p/BBu0Z0jLMK3/
Measuring radial runout: https://www.instagram.com/p/BB5wBLOrMH3/
He had another on grinding the shaft to final spec, which I can't find now.


As for perfectly aligned, or flat, or round, or parallel... there no such thing. Everything is done to some spec and nothing is perfect. The smaller you get, the harder it gets. Even heating something up a few degrees will change things as it expands.

If you want, I can share some tour videos from a few machining companies who rebuild spindles, lapping machines, and other machining tools. Parts can't be better than the tools which made them, so it's particularly neat so how they do things.
samuellaw178 wrote:On the Versalab, do you do WDT on your shots before the alignment?
Not WDT, but I did a distribution technique (mixed in a bowl, then dumped in).

We'll see what mine is like once it's back from Frank. He says no distribution needed anymore.
samuellaw178 wrote:I've read often enough that alignment makes a huge impact on Versalab's operation. My impression/guess was two fold - one is due the design and secondly the shaft runout was too much to begin with. On the design front, my impression was the Versalab has a static wiper underneath. If this is out of alignment, I suppose that will affect the distribution and retention(thus low EY). On a perfectly aligned Versalab, if you remove the wiper, does it have static, do you still need to distribute for high EY without channeling?
The complaint with the Versalab was the two bearings being next to each other, and the runout/clearances in the bearings would allow the shaft to move. Some argue the shaft will center itself within the bearing clearances. I think that's idealistic. Which is why Frank gives the extra lower bearing and uses tighter clearance bearings.

With the wipers, there are two:
- There is the static wiper (named static because it doesn't move). It's a little piece of wire which knocks the fines off the rotating flat burr.
- There is also the moving wiper. This knocks/brushes/blows the fines off the bottom funnel.

The wipers wont affect grind distribution (or do you mean distribution in the basket?), but they will effect retention. You need the wipers or much of the dose (33-50%?) would stay inside the grinder from static electricity. All grinders must deal with static electricity from grinding somehow.

Haven't measured EY with a Versalab yet. I got the refractometer after my accident.
samuellaw178 wrote:IAlso, 'cutting' is just a layman term as I do not know the right jargon. :oops: To my understanding, attrition is an imprecise process. Basically you have beans fracturing and 'exploding' if you will,to all sort of particle sizes. Then you're hoping the size distribution will fall into the right range with the right ratio, and course the burrs gap opening is helping with determining the grind size threshold. None of these seems like a precise process.
You're right, it's not a very precise process. Basically the beans are shattering, and keep doing so until they are small enough to fly out the burr gap. This is why you get a distribution curve and also why it's bi-modal.

Even with in a distribution curve. Wether it's done by laser diffraction or sieves, each has their merits and downfalls. Ground coffee is 3 dimensional, both methods only measure 2 dimensions. Think of a watermelon, and try to measure it. If you measure it from the end, it may be 30x30cm. If you measure it from the side it may be 30x45cm. When graphing the particles they're only using the longest axis, and the same shape/particle would "measure" very differently based on which side you use. So even with distribution curves, we need to take them with a grain of salt.

Beyond that, particles themselves are just a collection of cells. We extract cell by cell, not particle by particle. The whole "fines over extract" thing is a bit of a misleading truth. The outside cells of the boulders are also over extracted.

But I digress...