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I would like to know if ghost/crushing burrs produce better particle uniformity than conical burr grinders.

Ghost burrs are particularly not so popular in the US, but some notable brands are from Fuji Royal in Japan, and some steel-manufacturing companies in Taiwan.

Conical burr grinders are used by Breville and Baratza (at least the most legitimate ones). I particularly use the built-in grinder on my Breville, and the uniformity is great, but I'm attracted to the ghost-burr grinders by Fuji Royal and Yang-Chia (amongst other competing companies in Taiwan).

Has anyone owned either of these kinds of grinders?

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    I've heard of flat burrs, and of course conical burrs, but never ghost burrs, and my google-fu is failing me. Any chance for a link on more information on them? – Evan May 14 '16 at 23:59
  • @Evan, here you go home-barista.com/advice/… – wearashirt May 15 '16 at 8:59
  • The link you posted shows a flat and conical burr, as well as a hybrid burr which is a combination of both. Calling it a "ghost burr" is either a proprietary name or something someone just coined on that forum. Hybrid burrs are definitely a thing. – tsturzl Jun 2 '16 at 14:35
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In theory a hybrid burr set where a flat burr is followed by a conical burr would be ideal, combining advantages of both burr types. In practice though there are many confounding factors in grinder design and world class grinders can be found with all types of burrs. Some of the best grinders in the world made by Ditting is Switzerland use large precision flat burrs rather than conical burrs.

Conical and hybrid grinders are more expensive to manufacturer and are therefore less common in cafes. But that is not to say that a conical grinder like the Mazzer Kony /Robur is not a superb grinder just because it's flat disc burr brethren vastly outnumber it. It can be said that conical burrs are seen more often in higher capacity grinders. Some other well regarded commercial burr grinders include Cimbali, Mahlkonig and Bunn.

In practice though there are many confounding factors in grinder design and world class grinders can be found with all types of burrs. Some of the best grinders in the world made by Ditting is Switzerland use large precision flat burrs rather than conical burrs.

What can be said is that industrial production roller mill grinders put all of the burr grinders to shame, producing the best particle size uniformity of all. However these room filling behemoths, with similarly large price tags are impractical for use in cafes or even small to medium scale industrial coffee grinding where burr grinders dominate.

To answer the question posed then, no. Peg discs do not produce superior particle size uniformity than true burr grinders - conical or flat disc. Quite the opposite in well established by myriad reputable sources and can be seen in plots of particle size distribution.

The flat (non burr) disc grinder crushes /fractures coffee beans in a less predictable manner than precision burrs that have a more consistent and more sharply delineated size reduction path. Excessive fines can be thought of as unwanted dust arising as a byproduct from a less precise size reduction

conical burr (mazzer)
conical burr (mazzer)

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