The third and most recent development in coffee grinding is original to the age of electricity. Two steel blades powered by a small electric motor whirl at extremely high speed at the bottom of a cup-like receptacle and knock the coffee beans to pieces. With the burr method the fineness of the grind is controlled by the distance between the burrs, whereas with the blade method fineness is controlled by the length of time you let the blades whang away at the coffee. This makes the whole process a little hit and miss, unless you are so systematic you start timing the process.
If you aim for a fine grind with blade designs, grind in spurts of a few seconds each. It also helps to bounce the bottom of the grinder gently on the counter between spurts to tumble the partly ground coffee back down around the blades.
Blade Grinder Minuses. The disadvantages of blade grinders? Above all, they grind less consistently and predictably than do burr grinders. Even the less expensive burr grinders hold their setting well, and give you the same grind, day after day. Only the most attentive and compulsive among us are capable of achieving the same consistency with a blade grinder. For brewing methods using paper filters, minor inconsistencies in grind do not matter much. For plunger-style brewing, drip-brewing without filters, open-pot brewing, and espresso, all of which demand a more consistent grind for success, anyone who has taken the trouble to read this far will probably want the more predictable results obtainable from a good electric burr mill like the Capresso, Braun, Bunn, or Pavoni.
Blade grinders also cannot produce the extremely fine, powdery grind required for Turkish- or Middle Eastern-style coffee, for which, again, you need either a good hand grinder, such as the Zassenhaus or one of the specialized "Turkish" hand grinders that look like large pepper mills. The best electric espresso grinders usually work for Middle Eastern coffee as well.
Another minor drawback to the blade grinder is the difficulty presented in getting the coffee out from under the little blades and into a brewer. You face the same problem when you clean the grinder.
Blade Grinder Pluses. The advantages of blade grinders are more succinctly stated: They are cheap, grind quickly and do not take up much space in the kitchen. You also can use them to pulverize nuts and similar cooking ingredients, and, unlike burr grinders, they can be used with flavored coffees.