Types of Coffee Grinders
Blade grinders are inexpensive but produce a very inconsistent particle size. Even if you're trying to get a course grind, you will get some powder. Blade grinders are nothing more than little blenders that slice, tear, and smash the coffee beans. Worse yet ... since the blades are spinning at a very high RPM, it is very easy to burn the coffee. Using a blade grinder to grind just enough beans for a single cup is an exercise in futility. You'll have to experiment with any particular blade grinder to achieve the desired results. As a rule, you don't want to grind for more than 20 seconds. Beyond 20 seconds you risk burning the ground coffee. If you are grinding a small amount of beans, say for one cup of coffee, you should shake the grinder as it is grinding. When grinding three ounces of beans the blade grinder will produce the best results, because the aggregate produces good resistance to the blades and a natural flowing circulation of the aggregate occurs. Never try to grind more coffee than is recommended by the manufacturer.
The old fashioned hand grinders are excellent devices, and they only cost a little more than blade grinders. They are burr grinders, and have not been significantly improved upon since they came into existence . They're slow (about a minute for one cup), but they produce a very consistent aggregate, and there is no chance of burning the coffee. They are still made today, and size of the grind can be adjusted from very course to powder. There are burr grinders that are powered by electric motors, which takes the effort out and is faster.
Disc and Conical
Disc and conical grinders provide the most precise grinding. These grinders have serrations or grooves cut into the discs or cones. The coffee beans fall in between the two discs or cones, one of which turns while the other remains stationary. The sharp edges of the grooves are what cut the beans and result in the most consistent grind. These are the grinders of choice for high quality coffee, but they are quite expensive.
Warning Regarding The Grinding of Flavored Coffee
Never grind flavored coffee in the same burr, disc, or conical grinder that you use for straight coffee. The flavor extracts coat the grinding discs and are virtually impossible to remove. Flavor extracts in grinders will impart flavoring to straight coffee. Blade grinders can be cleaned, but you will discover that removing the extract completely from the blades, and the grinding chamber, is not all that easy.