64mm burrs with a pre-breaker vs. 83mm without

Grinders are one of the keys to exceptional espresso. Discuss them here.
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#1: Post by Ursego »

The question is spawned by an off-line conversation I had with an acquaintance. He claims that 64 mm grinder with a pre-breaker is roughly equivalent to a 83 mm one without (if not even better since the less the diameter the better the alignment). Of course, we are talking about burrs of a same kind, and a hypothetical situation (non-existent in reality) where the grinders are absolutely equal.

As he says, it's roughly how a 2 liter car turbo engine compares to a 3.6 liter atmospheric engine - a smaller number but the same power (there are nuances, but by and large they're about on par).

The explanation is simple: a separate pre-breaker does some of the work that would normally be done by the burr (specifically, by its inner pre-breaking zone), so all burr has to do is finish the work the pre-breaker started.

The pre-breaker is probably the reason why the Zerno has beaten all the other 64 mm grinders in this video. Because of the pre-breaker, this contest could be inherently unfair on Zerno's part.

In another video, the Zerno is compared to 83 mm grinders (and to the 78 mm Sculptor which has an even larger burr work surface than the 83mm because of the smaller internal hole), and that seems a more honest comparison. Specifically in this fragment, the author described how the Zerno soundly defeated the Niche Duo (both with SSP MP), contrary to his expectations.

What do you say, guys?

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#2: Post by Jeff »

Anybody that can make broad generalizations like that and believe them enough to spout them as truth is not someone I'd trust with any buying decision.

There are far too many other things impacting grind quality and subsequent cup quality.

Hypotheticals don't matter. You're buying a real grinder. Compare actual grinder/burr set combinations to each other.


#3: Post by malling »

Theoretical yes a prebreaker could have an effect, I definitely noticed a difference on 98mm before with and without and I also noticed a difference in the feedrate of said breaker but it was fairly minor more like a refinement.

Also there is the whole thing about are the burrs equally seasoned/broken in. How large a difference is there on alignment and runout.

The problem with comparing grinders is that in truth we are comparing the whole thing not just the burr and the prebreaker but the entire construction any sort of misalignment or movement is going to have an effect, just as retention, exchange rate and potential pregrinding will.

So it's easy to conclude it's down to the prebreaker but there is also a chance many other aspects influence on it as well.

Also we don't really have any sort of data that objectively can say if a prebreaker has the sort of effect. Additional the burrs uses are still the same design they haven't been designed with a prebreaker in mind.


#4: Post by Allongedaze »

I think the Zerno looks nice but it's getting overhyped by a lot of YouTubers.

I'd be interested in side by side taste tests with it using the same SSP burrs as other 64mm machines, as I bet it would be very hard to tell differences despite it potentially being a well built grinder with closer tolerances and an auger feed.

Maybe the blind burrs are even better because of additional surface area but again would most tasters be able to not only pick them out consistently but also say it's a significantly better tasting cup? I highly doubt it, again I'd guess it'll only be very marginal gains.

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Ursego (original poster)

#5: Post by Ursego (original poster) »

I understand that it's just a belief and it's an ad, but anyway:


#6: Post by malling »

I truly doubt added surface area due to no screw holes has any detectable effect. The holes don't really change the grind path or the grind length.

But it's nice for cleaning and removal


#7: Post by erik82 »

It's been shown years ago with the EG-1 and other grinder that screwless burrs have no effect on grinding, just a bit easier in cleaning. I personally even find burrs with screw holes better as the magnetic mount on most let's them move from left to right due to the play between the burrs and the burr carrier. With screws they can't move so it's even better for alignment. But looking at the Lagom 01 with screwless burrs that are mounted with screws from underneath is a much better design but will also have no real effect on grind quality.

Also the need for a pre-breaker isn't clear yet and probably will be the next couple of years. It may do something but I don't expect big differences. It's easy to say that a 64mm will perform like a 83mm with no further context. A LSM 83mm doser grinder with bad tolerances will also perform less then a DF64 with well aligned 64mm burr. And a good 64mm burr profile with low tolerances will also perform better then a 83mm traditional cheap burr. So without any context that claim has absolutely no value.

I do expect that the motor will be happy with a pre-breaker as it needs less torque to grind beans and so less chance of stalling which may be the only positive factor here. Same is true for those nice tasting Pacamara beans that bounce up and down on the burrs because they're so big and light. A pre-breaker will help feeding the beans to the burrs and result in a bit less retention.

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#8: Post by StoicDude »

Ursego wrote:I understand that it's just a belief and it's an ad, but anyway:

I'm pretty sure Lance Hedrick is the one that said this in his review.

If the prebreaker had such an effect, why not grind your beans with a handgrinder prior at its max setting and then feed to the grinder?

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#9: Post by Jeff »

Double grinding was explored a couple of years ago and has since faded.

Vertical burrs may have a meaningful impact. Controlled feed rate may have an impact. The impact of both, if any, seems as though would depend on the burr cut.

I don't trust anybody's marketing copy on this. Gevi is about at the bottom of the heap. Seemingly their biggest contribution has been the "Gevi burrs" people were buying off Alibaba ($17), seemingly from the ODM (which was not Gevi), and putting in grinders like the Urbanic.

Edit: It is likely to be a different thing to competently design a grinding system together consisting of an auger and a burr set (such as in the Bentwood) than it is to put existing burrs with their existing prebreakers after an auger. Dual-burr systems, such as the Versalab and recent Kafateks take this another step.

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#10: Post by another_jim »

The Versalabs and DRMs I tried had conicals that were too widely spaced to break beans. Used without the flats burrs, the beans just fell through them whole. The conicals act to force the beans into the flat burrs, which on the DRMs have no coarse grind section of their own.

Double grinding experiments have never survived the blind tasting trials. There is however a caveat ...

I know about two places double grinding is used routinely. First, to get a finer final grind on manual grain grinders; here the grind setting on the first pass is almost as fine as on the second. The second use is commercial roller grinders, which can have one to three rollers in sequence. To get fines free fine grinds, several rollers in sequence are better than just one.

These uses suggest that there may be something to double grinding that hasn't been tested properly. Double grinding by the same grinder gets finer grinds with less effort, but gives negative blind test results, and so no increase in quality. Multi stage roller grinders suggests that double grinding and prebreaking does have a quality effect, but only if it is done very well with separate burrs designed for the coarser and finer stages. I have no idea if the prebreakers discussed here are anything like as good as the first stages of roller grinders, but I'm somewhat doubtful.
Jim Schulman