Hi All,
Question :
Does a bigger burr size compared to smaller one with the same geometry improve the quality in cup? Considering maybe both are the same type of grinder, very similar burr geometry and both aligned properly (ie. Eureka 55mm specialita - 65mm XL/Zenith - 75mm Atom). Definitely can be other brands as well.
I'm not talking about in high volume situations, I'm just picturing a person trying to pull a couple of the best espresso shots.

Despite the quote from Hansung Lee (SSP owner) in my sig, I don't think that it is that simple.

For example, a while ago a few users went to the Compak R120 (120mm burrs), but I don't hear much about them now. Similarly, the Ditting 1203 is a rarity compared to the 80x. While machines these large have disadvantages in home use (the bag knocker on the R120!), I would suspect more people would have those grinders if the jump in quality from 98mm/100mm was there.

Also, it is hard to say "similar burr geometry." At the same rpm, a larger diameter has faster angular velocity. Are the designs still similar?

However, as a sweeping generalization, bigger flat burrs are often better, but size in and of itself may not be the actual reason.

Think of coffee. As a sweeping generalization, bigger beans are tastier than smaller beans. Entire country's grading systems are built on this, e.g., Kenya. However, it isn't the size itself, it is just that healthier beans are more likely to be larger.

TallDan wrote:Burr size is part of it's geometry. You can't have burrs of different size and the same geometry. It's as simple as that.

A triangle is still a triangle regardless of size.

As an aside, the large inner diameter of the Major burrs makes them 'smaller' than their outer diameter might imply. Dimensions here: Bigger burrs fact or myth? (in the cup)

So let's suppose we magnify an x mm burr by some amount y, keeping relative dimensions identical ("scale invariant geometry"), and also adjust RPM so that the angular velocity at the perimeter is the same. Would these two configurations behave identically?

That's the null hypothesis, and I'd say it's up to adherents of the opposing view to demonstrate some mechanism which would give rise to a difference in the cup / in the particle distribution.

TallDan wrote:But a big triangle is different than a small one. They can be substantially similar in many ways, but not the same.

80mm flat burrs and 64mm flat burrs are going to be different.

Bottom line though, it's probably an academic discussion with little practical value. Burrs are the most critical, but only one part of a grinder. If I can fit either 64mm or 80mm in my grinder, I'm going to want the 80mm, all else being equal. It's extraordinarily rare to have a grinder that can fit both, in part because there's not much benefit to putting small burrs in a big grinder.

If I'm choosing between a mazzer major and a lagom p64, I'd choose the lagom. But those two grinders have very little in common other than flat burrs and electric motors, even if those properties make them substantially similar.

So you would choose the Lagom P64 based on the intangibles rather than burr size...correct?

I think that the thing to remember is that nobody seems to know how to design burrs for taste. Tasting "boxes and boxes of burrs" seems to be the development process ... at least given public statements by Mahlkoenig/Ditting and Conte Valerio/Eureka/Nuova Simonelli/Victoria Arduino.

henri wrote:So let's suppose we magnify an x mm burr by some amount y, keeping relative dimensions identical ("scale invariant geometry"), and also adjust RPM so that the angular velocity at the perimeter is the same. Would these two configurations behave identically?

That's the null hypothesis, and I'd say it's up to adherents of the opposing view to demonstrate some mechanism which would give rise to a difference in the cup / in the particle distribution.

No, because the centrifugal force loading the burrs with coffee would be different.

In addition, the, for lack of a better term, triangles at the outer parts of the burr would be sized differently.