Shopping for espresso equipment from Internet sites can be frustrating. There are lots of options to choose from and many advertised performance metrics lack intuitive value (for example, motor RPM). To make matters worse, semi-anonymous consumer reviews vary in quality and objectivity, and it's not uncommon that some reviewers "shill" by placing positive evaluations of products they wish to promote. Although most fraudulent reviews are easily recognized by their unqualified glowing assessment that is inconsistent with other reviewers' experiences, it makes for tedious and time consuming research.
To round out this review and give you a defense against potential market hype, I'll begin by defining some commonly advertised distinctions between grinders; I've ordered them from the most intuitive to the least obvious:
Doser — a doser is the large cylinder in the front of the grinder that receives the grinds. At the bottom of the cylinder is a circle of wedge-shaped vanes that fill with grinds. Each flick of the handle advances the next wedge toward the bottom exit hole at the front of the doser. The dose amount is adjusted by increasing or decreasing the height of the rotating vane, thereby changing the wedges' volume. To work properly, the doser must be at least ½ full so the weight of the grinds pushes hard enough to fill the wedge from top to bottom. Metering shots using a doser is thus practical in a busy café, but for home use the doser instead acts as a "holding area" for a shot or two worth of grinds that are then dispensed by pulling the handle a few times.
Doserless — as the name suggests, a doserless model delivers the grinds directly into the portafilter or other container. Home espresso aficionados regularly debate the merits of doser and doserless grinders. I've owned two doserless grinders and one doser grinder. As long as the doser efficiently sweeps the chamber clean and the grinder is fast, I am content to work with either design. It's true that a doser is more practical in some ways because you are free to do other things while waiting for the grinder to finish; with most doserless models, you must watch over the portafilter while it fills. The Mazzer Mini Electronic Doserless grinder, which includes a portafilter cradle and timer-controlled measure, is a "hands free" exception.
Adjustment mechanism — five of the six grinders in this review have a stepless adjustment, or infinite adjustment as it is sometimes called. The term "infinite" may give you the impression there's a huge, practically unbounded level of adjustment, but in practice, the range for espresso is relatively narrow. Macap offers an incremental / stepped adjustment mechanism. A pin locks into one of the closely-spaced holes on the underside of the grinder's collar. For the six grinders under consideration, the total range of practical movement for espresso grind is about one to 1½ inches of rotation of the grinders' adjustment collars. Typically "dialing in" a grinder involves very small rotations of only a few millimeters. The individual grinder sections will discuss their respective adjustments in more detail.
Burr Size — in general, larger burrs and a more powerful motor means greater grinding speed. The greater burr surface area allows for more cutting edges, decreasing the time required to grind the same amount of beans. Under load, larger burrs will also resist heating up longer, hence why the Cimbali Junior with its 64mm burrs is deemed a full-time grinder while the standard Mazzer Mini and Macap's 58mm burrs make them more appropriate choices for a café's secondary grinder. The Mazzer Mini E Doserless grinder has 64mm burrs and the same motor as the standard Mini (the manufacturer recommends 30 seconds of rest for each 20 seconds of use to avoid overheating the motor).
Weight — in a gross sense, weight can be treated as a proxy to material quality and motor capacity. Consider the weight of the Cimbali Junior (34 pounds) compared to the Mazzer Mini (standard Mini is 22 pounds, doserless is 20 pounds) and Macap (20 pounds). We can attribute a significant amount of Junior's additional weight to its heavier motor and larger burr assembly, again explaining why it's rated as a full-time commercial grinder.
Motor Speed — the faster a grinder motor spins, the more likely its burrs' action will generate enough heat to damage the coffee's delicate oils, or worse, impart a burnt flavor. Therefore the manufacturer chooses a balance between burr size, motor speed, and desired grind time. The motors of all six of these grinders operate at 1600 RPM. Some advertisers will point out the benefit of a particular grinder's slower motor speed; keep in mind that there's no "better" motor RPM, but rather the appropriate ratio between burr design and motor speed.
The last three metrics may interest an engineer, but many consumers struggle to relate them to anything meaningful. To make it easier for you to navigate your selection between these six excellent grinders— indeed, each of them is a great choice for different reasons —the Conclusion presents a group of practical criteria for your consideration beyond the list above.
Home baristas regularly debate the merits of doser and doserless grinders. Arguably a doser is never used for its intended purpose in a home environment (i.e., measuring out a predetermined amount of coffee) because the chamber must be at least half-full so the weight of the grinds is sufficient to accurately fill the "pie wedges" formed by the doser vanes. Instead the doser acts as a staging area for the grinds exiting the chute and the vanes simply push them towards the drop hole at the front of the grinder into your awaiting portafilter.
However, the doser isn't entirely superfluous. If you've ever attended a barista competition, the frenetic "thwack thwack thwack" of the doser handle almost blurs into a continuous buzz. One explanation for the baristas' behavior, besides nervous energy and way too much caffeine, is that the advancing of the doser vanes helps agitate the grinds exiting the chute. Baristas using a doserless grinder cannot "mix things up" until the grounds reach the portafilter. As a quick comparison of the visual difference, see the two loosely filled baskets pictured above. The surface of the grinds dosed "competition style" on the left appear free of clumps compared to the grinds from the doserless model. However, whether this added mixing is consequential is questionable, and I didn't note an in-cup difference given a well-practiced dose-distribution-tamp.
Ultimately the choice of doser versus doserless is a matter of preference and the premium you place on convenience and neatness. In that regard, the Mini E Doserless is beyond reproach.
Some espresso purists insist one should only change the grind to correct a too fast or too slow pour. I believe you'll have better results by watching the pour instead of a stopwatch. Regardless, given the emphasis on precise 25 second pulls that dominates online discussion boards, it is worth noting several techniques for those who wish to compensate for small differences in pour times between two of the Macap's steps:
This is the straightforward way of dealing with it: Put the timer in the drawer, watch the stream color and cut off the shot when it blonds. If it isn't widely off mark time-wise (i.e., less than 22 seconds or greater than 32), it is close enough. In other words, let your taste be the judge and "Trust the Force, Luke."
This suggestion may raise a howl in some quarters, but increasing the tamp pressure by 10-15% adds about 2-3 seconds to pour time.
If changing the tamp pressure from shot-to-shot offends, instead increase the tamp pressure for all shots. The "hard tamping" barista sees a smaller pour time change between two increments than a "light tamping" barista.
Fill the basket a little over halfway, tamp lightly (say 5-10 pounds), finish filling, then tamp as usual. You'll add a couple seconds of pour time.
A couple more grams of coffee adds around 2-4 seconds, depending on the fineness of the grind and the moisture content of the beans.
Grind half of the shot, stop, move the increment up/down one notch, finish.
The principle advantage of an incremental adjustment is the ease of re-finding widely spaced settings, which appeals to those who frequently change between different types of coffee preparations. The Mazzer Mini is certainly capable of moving quickly between espresso and French press grind settings, although it requires a firm two-handed grip. The worm drives of the Cimbali Junior and Macap M4 Stepless are ideally suited for minute adjustments of a dedicated espresso grinder.