For most coffee enthusiasts this could be obvious but for newbies like me it was unexpected although seems very simple and logical.
Good grinders with conical burrs are more difficult to make right as one has to worry about making the halfs strictly coaxial which is more difficult than making them strictly parallel.
More here:
https://perfectdailygrind.com/2020/05/c ... ifference/

Interesting read. One thing that caught my eye in particular (from the article):

with flat burrs, only parallelism is important

Is this really true? It's not clear to me that being significantly out of axial alignment wouldn't also have a negative effect. At least on grind speed, but also possibly on the particle distribution.

henri wrote:Interesting read. One thing that caught my eye in particular (from the article):
Is this really true? It's not clear to me that being significantly out of axial alignment wouldn't also have a negative effect. At least on grind speed, but also possibly on the particle distribution.

If you misalign 100 mm burrs by 0.2 mm the grounding surface would decrease approximately 16 sq.mm which is relatively very small number. I do not see what else would affect the grinding process.

Very good article. Thank you for posting. I've become rather confused and curious on how these two burr types affect flavor and mouthfeel differently. I have been wondering if it is worth getting a high end conical to try out to see if it might compliment my flat burr grinder that I love. I'll get an opportunity to experiment since an HB member so graciously has given me a new burr set to try out. These burrs, while being flat offer a bimodal grind which is similar to a conical burr.

This morning I listened to a lengthy and excellent podcast with Douglas Weber from Weber Workshops on this topic. One of many things he said that stand out is that it is easier to get a very good shot with a conical burr set than it is with a flat burr grinder. He compared his new Key grinder (conical) to his EG-1 (flat). In short, the flat burrs in the EG-1 (which I'm very familiar with) will yield a more precise extraction than a conical set. Flats are unimodal and grind to a uniform size. Conical on the other hand is bimodal meaning that the grind size is not uniform and is more forgiving in it's shot. He compares flats as being like driving a Lamborghini vs a Bentley. The Lamborghini is going to be more exacting with finer controls than the smooth, forgiving ride of the Bentley. In other words, it will be harder to dial in a flat grinder, but once done it will be more precise in pulling out the nuanced flavors of the beans than a conical. Which one is better? He wouldn't say other than it's subjective to each person.

While I'm far from being an expert at this, I can say that I haven't found my EG-1 hard to make great shots quickly and it has been fun further experimenting to see just how far I can take it. For what it's worth, I really like driving a sports car too.

As a marine engineer and machinist I'm not buying into the explanation of difficulty of the alignment of the conical burrs.
Yes, I suppose there may be other factors in play but I don't see why alignment should be such a big problem for conical over flat burrs. I see enough examples of other machinery and pumps that prove the contrary.

I also agree with baldheadracing in that that article seems pretty biased.

karamba wrote:If you misalign 100 mm burrs by 0.2 mm the grounding surface would decrease approximately 16 sq.mm which is relatively very small number. I do not see what else would affect the grinding process.

Methinks it's more like 30mm² of ≈900mm². The grinding portion of the burr is the outer ring, the inner portion is breaking. Whether it makes any difference is debatable.

IMO, the article is bunk.

BSdV wrote:As a marine engineer and machinist.

Your qualifications are extremely impressive but as a rule of thumb it is better present facts to support your point.
Just for the reference the burr alignment procedure Here: http://www.youtube.com/watch?v=5BkPYedHXE0 seems completely lame to simple mortals like me. One has to be a marine engineer and better yet a machinist to align burrs by eye and finger touch.
As for the biased article, maybe, but I did not notice that. The guy does not state that flat burrs are better, just the fact that it is easier to make them.

The article covers many aspects and seems pretty balanced to me. They provided one specific technical reason (easier alignment thus better grind distribution) for choosing flat over conical. If their logic is flawed, I'd like to see a better argument than "they are biased because they chose flat".

karamba wrote:The guy does not state that flat burrs are better, just the fact that it is easier to make them.

Marco Beltrame, Coffee Trainer and Technician at Dalla Corte, wrote:In fact, he believes that flat burrs will always outperform conical burrs.