Is alignment an issue on actual commercial grinders prior to burr changes or burr wear?

If the axes of the two burrs are aligned and properly fixed, wouldn't wear realign uneven burrs? (Seems to have worked with lots of medieval grain mills).

MWJB wrote:Sorry Rich,
You've lost me here, I think you might be reading the chart wrong? The x axis is % volume, not the grind particle size.

Rich

I was looking at the semi-log data plot that has been referenced on this thread and discussed and wondered what it would look like with a linear scale instead, so I decided to make a crude attempt at converting some of the data points to a linear plot for comparison. Here's the original: http://payload236.cargocollective.com/1 ... Graphs.jpg

I decided to take data points only at the marked intervals on the scale as shown in the table below. This really distorts the chart and even changes the peaks because the sampling size is much larger than the peaks for these graphs, but I believe that this does give me some feel for the differences in particle distribution between the grinders which are hard to see on a logarithmic scale.



In order to do this, I copied the Y axis scale and moved it along the graph to rough out the data points at each of the marked points on the particle diameter X axis. You can see how crude this is.



The resulting graph shows the distorted linearization of the original graph, but does give some flavor to the distribution of the main grinding mode for each grinder for the grind settings used in these graphs. The EK43 does look narrower.

Nice work Yakster, thanks.
It seems, then for me to put it into words that the squat form of the EK43 indicates an interval where there is more of a certain range of particle sizes but less overall variation... the taller curves (especially the K30) would indicate more variation overall but a greater percentage of grinds are at the "target" amount.

another_jim wrote:Is alignment an issue on actual commercial grinders prior to burr changes or burr wear?

If the axes of the two burrs are aligned and properly fixed, wouldn't wear realign uneven burrs? (Seems to have worked with lots of medieval grain mills).

Not sure about the first part but do think that the precision folks expected/required to mill grain in the middle ages is quite different than what we expect from a coffee grinder for espresso
Not that I have a clue about the effects of intolerances on burr sets and how they are typically aligned yet when I read that Mazzer says they aim for 0.02 mm that sounds as if there is little room for play (might also be that unaligned burrs wear much faster while the result in the cup does not change that much).
Don't think alignment can be checked in a simple way other than with the marker method.

Weren't laser sizers too inaccurate for ground coffee since they assume spherical particles or some such?
TGP II: Particle Distribution Analysis of Grinder Adjustments - Interim Results

another_jim wrote:Is alignment an issue on actual commercial grinders prior to burr changes or burr wear?

If the axes of the two burrs are aligned and properly fixed, wouldn't wear realign uneven burrs? (Seems to have worked with lots of medieval grain mills).

The short answer is no. They're off by far more than they'll ever wear.

Many of the grinders I've measured are off between 50-75um axially, and around 10-50um radially. I'd love to hear others chime in with what they've measured.

As for how much burrs wear before they're considered old and worn, everyone has a different threshold. But for reference most TiN coatings are around 5um thick, and how often have you seen the TiN completely worn off the burrs? Most people replace them before that.

nickw wrote:Many of the grinders I've measured are off between 50-75um axially, and around 10-50um radially. I'd love to hear others chime in with what they've measured.

Interesting, that's about 1/4 to 1/3 of the normal spread in particle sizes. The obvious takeaway is that a well aligned grinder would recover that margin in a tighter spread.

Bluecold wrote:Weren't laser sizers too inaccurate for ground coffee since they assume spherical particles or some such?
TGP II: Particle Distribution Analysis of Grinder Adjustments - Interim Results

According to Randy Pope in the talk listed, when you get to espresso the laser size analysis is the only good way. He talks about it from 9:15 - 12:00).
http://nordicbaristacup.com/2013/09/nbc ... pope-bunn/

As for shape, I've heard it said that conicals or more like likely to particles which are cylindrical in shape, but I can't confirm.

another_jim wrote:Interesting, that's about 1/4 to 1/3 of the normal spread in particle sizes. The obvious takeaway is that a well aligned grinder would recover that margin in a tighter spread.

Yes, it would help. Some before and after analysis would be very interesting (ideally with 3 different roasts: light / med / dark) as alignment will affect each differently.

I should note, that some grinders can be off far more than that:
Here's one forum member, who was frustrated with his grinder. When he finally measured it he discovered his lower burr carrier was out by 254μm axially.
Manufacturer tolerances for axial runout

Regarding alignment and taste:
When I measured my stock Versalab it had about 65μm of axial runout, through cleaning and careful reassembly I got it down to about 15μm (truth be told, it could be better still). To be honest, I was surprised how much better my coffee tasted after alignment. To the point where without saying anything, many of my non coffee geek friends noted my coffee tasted better.