Burr Quality Control

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

#1: Post by ira »

So last week I ordered new burrs for the Rocky I use for drip. Even before they showed up I got an email saying there had been a problem in that batch and to return them. But I decided to pull the grinder apart and clean it up anyway just to see how the new burrs compared with the old ones. The originals that came out of the grinder clearly had the Rancilio logo on them and measured with my Mitutoyo digital calipers they were perfectly flat with both burrs being the same thickness and having zero indicated runout. The new burrs were over .015 thinner than the originals, were different from each other by .0015 and one had a burr on it so it would not have sat flat. And to boot they looked about as dull as the 2 year old originals. My fingernail would not catch on any edge of any of the 4 burrs. And I was told they are made by the same manufacturer as the Duranium burrs.

So, am I the only person who looks at the burrs they get? If we started looking at them and sending back the ones that are clearly of inferior manufacturer might we have an effect on the quality of burrs.

Or am I overreacting and it doesn't matter? But how could it not matter if replacing used burrs improves the quality of the beverage? I just don't understand.


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#2: Post by Arpi »

My guess is that it could like the aftermarket parts in a car. Someone is out there that can make the "same" part cheaper. Lowest bidder gets the contract or they found a cheaper alternative that works the same. Could be many things but sounds like OEM versus aftermarket. From what country are the new burrs made?


ira (original poster)
Team HB

#3: Post by ira (original poster) »

Italy as far as I know.



#4: Post by Phaelon56 »

1) I do think you're overreacting

2) They are made in Italy

3) The original supplier for these burrs (I am the vendor who sold them to Ira - I buy from a large wholesaler) acknowledged that they are thinner but believed that they should work correctly. The first pair I sent out went to a friend who had issues with functionality - I proactively brought back all remaining sets at my expense.

4) The supplier told me that they come from the same folks who make the Duranium burrs but also considers that source to be producing better burrs (at this point in time) than the ones that come from Rancilio with the Rancilio name on them. I have found this supplier to be consistently honest, reliable and to be an accurate source for information.

5) I suggest that you find a source for the Rancilio burrs that are supplied by Rancilio, and do a careful inspection of those - I'll be curious to see what your results are.

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#5: Post by stefano65 »

for whatever it is worth, here is
another vendor's (me) point of view,
I don't have any affiliation with this transaction,
but I buy burrs myself sometimes directly from Italy, sometimes from a distributor.

I USED to buy rocky burrs from Rancilio USA which came from Rancilio Italy, which came from whomever the maker is.
The VERY last time I've did that:
all the dozen or so sets had marks on the screw holes and some of them where even dirty with coffee
to me they were clearly used or at least tested which I never heard of anybody else doing with burrs
now my point was with them:
I don't feel comfortable selling them to end users in this condition,
I return them all and decide never to buy "original" rocky burrs again.

now my question: which person that would have received a set of burrs as I described above would not think that they were used???

I choose for my customer the lesser of the possible issue (minor variances versus possibly used)
And, by the way, being a little thinner in the height is not an issue

A lot of people adjusting grinders use numbers on stickers of the collars, which should never be used as final indication but only as a reference when resetting the collars after a deep cleaning
Stefano Cremonesi
Stefano's Espresso Care
Repairs & sales from Oregon.


#6: Post by Phaelon56 »

Stefano's comment on the current situation with burrs sourced directly from Rancilio mirrors what my source said. He also advised me that new burrs (this is not true of Duraniums) usually need to be "deburred." This is a process typically described as the "breaking in" period and is a well known requirement for the conicals used in Roburs. There is a sort of conditioning or hardening of the surface that occurs in the molecular structure of the burr surface - I think from the heat and abrasion of the initial usage period. I don't pretend to understand the science and most likely have botched my explanation, but know a similar process occurs in polyester screen printing fabric during its initial usage period (factoid retained from a previous career).

I was told that many commercial burrs are "deburred" with a process that is done using some sort of tumbler or device/system that simulates the initial break-in occurring from coffee, but it is not done with coffee. He theorized that these new Rocky burrs may not have had this advance "de-burring" - possibly due to their small size.The one person I spoke to who tried them admitted that he could dial in his grinder, albeit to a different numerical setting than before. He described serious channeling issues suddenly seen in his shots, but did not want to try a "break-in" period to see if it got better. I don't blame him for that and simply did the refund instead.

Close-up visual inspection, micrometers etc. do not answer the most fundamental question. Do they grind properly and how do the shots taste. I regret that I do not have a Rocky grinder with which I can test this. If any of you have a Rocky in decent shape and want to do some kind of a swap for a cosmetically imperfect but highly functional Super Jolly - let's talk and then maybe I can test these burrs myself!

ira (original poster)
Team HB

#7: Post by ira (original poster) »

Well, After going through this with Robur burrs I recently received a new set of Mazzer manufactured Robur burrs and while you'd never mistake them for an end mill, it's clear they decided to clean up their act and they are actually sharp and have real edges. So Mazzer thinks it matters for the Robur and I'd guess if someone ever made decent burrs for things like the Rocky we'd either discover it matters or that they last a lot longer. I guess it's also possible that we'd find it doesn't matter but I doubt that.


David R.

#8: Post by David R. »

While I would be a little suspicious of burrs with coffee on them, it is certainly possible for one set of burrs to be slightly thinner than another and both be 'official' factory parts. I've owned Italian cars for 30 years, and still own one today. When I buy replacement parts, I never expect them to fit exactly as the ones they replace, even if I'm buying from the manufacturer. For some products, especially those made of porcelain or aluminum, there is (or used to be) a tradition of farming the job out to several small family shops or foundries that would make a small batch to their specifications. I do not know to what extent this still holds, but it is an interesting industrial model. It was also a testament to the skill of the craftsmen there how closely such parts do match, even when they came from different foundries.

As a result, while the quality of such manufacture is almost always very good, it is often not very consistent. In the case of burrs, as long as the grinder is capable of adjusting down, what matters is not the burr thickness but the burr quality.

Owen, I do happen to have a spare working Rocky sitting in a box in the closet, but (a) it is very very old, I think the second one ever discussed in an internet forum (which gives it some historical value), and (b) I already have a cosmetically imperfect but highly functional Super Jolly. It doesn't seem worth shipping two big hunks of metal 5000 miles each to satisfy a bit of curiosity!
David R.

ira (original poster)
Team HB

#9: Post by ira (original poster) »

I wasn't actually trying to get into a fight here, and I didn't bring up Phaelon because the problem has nothing to do with him. I was just broaching the question about burr quality using that as an example.

My Rocky is almost 2 years old, it grinds 26 grams of coffee per day plus a few pounds for parties so the burrs are probably due for a change. I would expect to visually be able to see some difference in the apparent sharpness of new and old burrs.

My new Mazzer Robur burrs appear to have sharp edges as do my Macap M4 burrs. My old Rocky burrs look quite worn out as did the new Rocky burrs.

I've heard many times that new burrs should be sharp enough to catch a fingernail. Neither the old nor the new Rocky burrs are capable of that. Is the fingernail test valid?



#10: Post by Phaelon56 »

Ira - I know you weren't trying to start a fight you didn't. Instead I think we're having a productive discussion. When it comes to burrs, I don't think you can really catch a fingernail on Super Jolly or Major burrs - not on the previous generation (the D series) or on the new ones (the M series.) It has also been my experience (with those burrs - I have no real experience with other burrs) that such burrs can be worn enough to make a difference in shot quality yet still look pretty much the same as a new set in terms of apparent sharpness.