First of all, the coarseness of the grind will determine how fast the water passes through during brewing. The finer the grind, the more time it takes the water to be forced through the grounds. Think of water flowing through a layer of sand as opposed to rocks.

This brew cycle time makes can make drastic differences in the taste of your coffee. It’s just like cooking and the brew cycle is the baking. You wouldn’t under or over cook a cake and expect it to taste the same.

Cheaper grinders don't always have coarseness settings, so you will have to experiment a little to establish how long to let your machine grind to achieve the right coarseness (or fineness, depending on your point of view).

The terms can be open to interpretation (just how fine is extra fine?) These comparisons might help you gauge your grind a little better:

• Coarse - Very distinct particles of coffee. Like heavy-grained kosher salt. Downright chunky.

• Medium - Gritty, like coarse sand.

• Fine - Smoother to the touch, a little finer than granular sugar or table salt.

• Extra fine - Finer than sugar, but not quite powdered. Grains should still be discernable to the   touch.

• Turkish - Powdered, like flour. Most inexpensive (blade) grinders will be unable to grind this finely.

 

A good coffee grinder will grind the beans very consistently and efficiently. You want consistency for even extraction. You want the grinder to be efficient so that very little heat is generated which will alter the taste of the coffee.