I've put this post in the Knockbox forum, since it's
not an espresso grinder.
I became fascinated with large burr, regular coffee grinders after my cupping session, two years ago, at Terroir.
They use a large Ditting grinder with 125mm burrs, which produces exceptional clarity for brewed coffee. The reason may be that the grinder produces almost no fines, a fact that becomes apparent if you attempt to use it for espresso. I didn't want to spend $2000 on that grinder, so I decided to take a flier on the Country Living Grain Mill, which costs $400, and had a good aftermarket on Ebay in case it didn't work out.
As you can see:
it even makes the titan grinder burrs look like puny little whirly blades.
The burrs fit into a cast iron manual grinder which can crank out 15 grams of coffee for french Press in about 25 seconds. Unlike most manual grinders, the huge flywheel takes almost no effort to turn.
The burr is worth a closer look:
compared to the static burr on the M3
The bean breaking (vertical on the M3) and coarse grinding sections are quite similar; but the fine grinding section is very different. The grain grinder has a long and gradually narrowing fine grinding section that does not quite end in a flat ring, while the M3 burrs are shorter and end in a ring. The grain grinder is designed to produce a single mode distribution of fine flour, and the M3 a dual mode distribution of coarse and fine coffee particles.
The grinder layout is simple, like all industrial grinders, with a horizontal axle and vertical burrs:
The pictured augur forces the coffee beans into the coarse grinding section. The rotating burr is fixed to the drive shaft with a key. It is spring loaded, and tightening the grind with the adjustment nut compresses the spring. The system is efficient, but not entirely free of waste. For brewing coffee, roughly half a gram of coffee remains as broken bits in the augur or as ground coffee stuck in the burrs. As one sets the grind finer, grind speed slows down and the amount of waste rises, since it becomes more difficult to force the beans through the burrs. The grind setting nut can loosen during grinding, especially for finer grinds, and it's a good idea to lock it in place with a 5/8th inch wing nut.
So how does it perform? I've compared it with my other grinders for brewed coffees. It is not always the best, but it is always close to the best and much more consistently so than my other grinders. The reason is simple to find, but hard to understand. On my other grinders, the best French press coffee required grind adjustments - some coffees did better ground a bit finer, others a bit coarser. The grain mill on the other hand was pretty much consistent at any grind level that felt like a French press grind.
The titan espresso grinders were a lot less finicky than the smaller espresso grinders, so maybe this effect for brewing is similar. Since one cannot fine tune the grind when cupping, the grain grinder is the best choice, and the one I've been using for the past six months.
On espresso it is not quite as hopeless as the big Ditting, but you still have ot wait 20 seconds before seeing the first drop on a non gushing shot. The grinder does produces some fines, since the rotating burr can wobble a bit due to its simple keyed mount of the grind shaft; but it is not enough for reasonable espresso use.
I think this grinder is worth checking out for people who do a lot of cupping, especially since it is easily motorized. But sadly, It is not the mythical, ueber-titan hand powered espresso grinder.