So, this was a reply to an IM that I wanted to put out there for public review, comment, criticism. I'm a risk taker and well versed in saying "oops. oh well." However, I'm pretty sure this is sound advice to those just not getting grinds fine enough from their grinder. I've done it myself and am happy with the results.

Since burrs and their mounting surfaces are all machined less than perfectly square (every machined part ever made, to greater or lesser degrees), and the tolerances all add up to them being out of parallel, I think the best bet is just zeroing the burrs so they hit and let them hit until they grind each other into submission. It's only the outermost edge in spots getting knocked down, so none of the cutting edges leading to the final mm or two are affected. That said, any flat burr grinder should be able to choke any machine as long as it's possible to zero it tight enough. I wouldn't do this at all unless the grinder just isn't getting fine enough for your needs since it is possible on some small scale that final cut affects grind performance at coarser grinds.

Yes, I'm saying run your burrs into each other to get them squared tight... or rather just keep moving them closer together until the coffee is ground as fine as desired, awful sounds be damned. Why not?

Your post is an interesting one, and I bet although controversial, it would make some people rethink burr edge parallelism. Here's a mental exercise I've been working on that I can easily get flamed for, but I'll mention it anyway.

For the last month now, while I'm completely rebuilding, repainting and modifying a Mazzer Major, I've been thinking along the same lines. I bought new burrs, and I've modified the doser quite a bit, and will add things down the line as I get it dialed in, but the main thing I've considered is playing with these new burrs to see if I can get them optimized right out the gate.

Mazzer micro bead blasts all their burrs, they have for several years now. But, that's somewhat insignificant since they're not mounted to my grinders burr mounts and motor shaft, places that can and do have their own flaws in parallelism.

I'm a knife and straight razor geek, who nerds out on the sharpening of those tools. I have a great deal invested in my sharpening gear alone. I've been considering a break in tweak that should theoretically really improve the burrs final edge parallelism. I have a diamond micron spray that is used on fine cutlery and straight razors, right before final stropping of razors. I'm kicking around the idea of taking some of my saved stale coffee that I have saved for the purpose of dialing in the whole project when it's finished. I can easily spray some on a batch of beans and let it dry, set the grind talc level fine, and run it all thru, then simply take everything apart and clean extremely thoroughly. It's not a mainstream idea, and would probably incite all sorts of flaming, but I bet it would achieve the end result a lot better, if the initial parallelism isn't grossly out of alignment to begin with.

Running the dry burrs against each other will create plenty of friction and heat, and some wear. Some ultra-fine abrasive would probably work a great deal better to micro-align all the uneven areas due to the non parallel alignment issues of the burr mount, shaft etc, everything that could affect extraction. Maybe even doing it after running the burrs against each other to do the initial flattening alone? I don't know, and I'm only guessing in the dark so far. The abrasive would affect not just the last edge of the burrs where they touch (like it would in just running them against each other) but also most of the cutting surface.

I think this would be an easier task to get great results out of a flat burr. And since the burrs are only about $60 new, not a major expense. If it screws up the burrs (and I sorta doubt it) it's not a big deal for me.

This whole mental exercise would likely fail however, if the burr mounts/shaft are grossly out of parallel. I would need DSC's or Frank's level of tooling to measure the run out to even have a clue, so I'm not posturing this as any kind of clever idea, just an idea. Even very small deviations in parallel would likely not be affected by doing something like this, and if care wasn't taken, I'm sure I could do more damage than good if any residue made its way down the motor shaft, but I'm fairly confident that could be avoided. But the idea of having increased parallelism between the cutting surfaces, mounted to my burr mounts, and on my grinders motor shaft, seems like something that couldn't really be achieved any other way than just a lot of use and slow break in.

Well, I wanted my ek to give me 40 second shots without resorting to reduced pump pressure (which I think is a totally valid option)... Not exactly a $60 mistake potential.... I think these burrs are a bit more than that. But I did it and now I can choke my gs/3 with city roasts. Goal achieved. Taking the burrs out to inspect afterwards, it's obvious how little material had to be knocked down and how inconsequential running the burrs into each other is.

I think the level of precision the ek would have had to have for my goal would have been an unrealistic expectation out of the box. Wide burrs multiply the required precision.

I'm not sure if you've seen this post, but they made a minor adjustment to the burrset:

http://grindscience.com/2015/02/just-testing-ftw/

(It would be interesting if someone more knowledgable than I could comment.) Anyway, I was considering - and not looking forward to - swapping my burrset, but this could be an alternative. I'll probably open mine up, clean it out, get everything adjusted perfectly, and give it a go.

Well, whilst it may have given you a suitable result, I cannot bring myself to accept this to be a valid method of rectifying burr misalignment .
As an engineer, I can only imagine that what you have done is dull the critical fine cutting edges on one burr only,..and not even evenly on both.
You certainly will have had no impact on the root cause of any misalignment , and I fear what you may have done is simply increase the percentage of fines in the grind produced which would affect flavour profile in various ways.
There are better, more permanent, ways of dealing with burr alignment.
But,..if you are happy with the result,...all is well

I'm also an engineer. The edges affected represent an inconsequentialy small portion of the total... Say five to ten degrees of three sixty. And because they are the narrowest exit path for the coffee, the least likely to impact the grind quality. I had spun the burrs to all three bolt hole alignments and determined the burrs themselves to be out of parallel, since the high spot followed the burr vs. the mounting surface, so while I could have had the back surface of the burr re ground, the combined expense of time and labor didn't add up. Running them together cut exactly the problem spot. Actually seeing the resulting scuff marks would illustrate how minor the problem was. I'm also a fan of just getting things done vs worrying about perfect when perfect isn't exactly necessary.

I'm wondering... And I'm just posing the question in light of this thread, since I don't have the answer.

Could this issue of misalignment, and letting the burrs "correct" themselves, be the underlying cause of what we colloquially call the "burr break-in" period. On HB, and the other forum, many advocate for seasoning burrs. In some cases, that means 20 lbs or more through new burrs to achieve good results. Some even use instant rice, of which the merits are endlessly debated.

I know my K10PB needed "breaking-in". I was getting inconsistency, channeling, and underextraction like crazy when I first got it. Now I get great pours virtually every time.

So did I inadvertently correct a misalignment problem while "breaking-in" my K10PB? Or, is burr seasoning a separate and still legitimate issue?

Or could it be a combination of both with new grinders: The need to season burrs AND correct misalignment?

NoStream wrote:I'm not sure if you've seen this post, but they made a minor adjustment to the burrset:

http://grindscience.com/2015/02/just-testing-ftw/

(It would be interesting if someone more knowledgable than I could comment.) Anyway, I was considering - and not looking forward to - swapping my burrset, but this could be an alternative. I'll probably open mine up, clean it out, get everything adjusted perfectly, and give it a go.

This is interesting and I wish I had the updated burr set prior to buying a second grinder. I have used two different ek43s and the first was unable to pull a shot longer than 20 seconds. Tis could have been due to extreme uniformity or burrs touching on one edge and keeping the majority of the particles from being small enough to resist flow. I can only speculate at this point since the second one will produce flow rate that are more acceptable for espresso. It just wasn't producing the flavor that I liked with the crema.

I am not sure I agree 100% with the topic of the thread but I will say that it seems like it depends on how out of parallel the burr is. Minor alignment issues may make this worth it since the reshaping of the burr might not have an impact on the shape of the particles extracted from different parts of the burr but it seems like the issue is being tackled by solving the wrong problem. The EK is amplifying this issue though since it has issues getting fine enough to get the flow rate within an acceptable range.

I would not recommend this as a first option for the average consumer. The integrity and alignment of the burr carrier assembly on your EK is not representative of the average grinder, commercial or household.

The success of this would vary greatly depending on the degree of misalignment and stack ups between the upper and lower carriers and the tolerances of the burrs themselves. If the burr carriers are not held absolutely parallel, the tooth depth on the fixed burr will never be equal around its circumference. In a industry where consistency is paramount, this would still be very inconsistent. You may now have a solid contact patch around the outer burr surface faces, but the size of the burr exit openings will still vary as the surfaces are not held parallel.

I would use feeler gauges and mark the runout of the burrs first. If indexing them doesn't fix it (assuming all surfaces have already been cleaned, deburred, and alignments checked) only then would I attempt this with the understanding that I might be placing an order for a new burr set.

Then again.. I have no idea what kind of tolerances grinder manufacturers design to, so my concerns may well be unfounded. Misalignment may be something the designer factors in and may play a positive contribution to grind quality. I simply don't have enough information.

I like your style mate, I have also thought about this and used it on an old grinder to great effect. I'm too scared to do it to the EK for reasons mentioned here but I do have my old coffee burrs sat around doing nothing.

Is there any mileage in mounting the burrs face down and then running them together or would that just make things even worse, my head can't work it out.....

I really is one of my main bugbears with grinders. It seems to me that the burrs should touch all the way round and if they don't then you are potentially grinding way off the mark by espresso standards.