Grinding your very own coffee is a great way to get the freshest cup of coffee each and every morning. Keeping beans whole right before turning into coffee grounds ensures freshness of not just the finished cup, but the beans themselves.
Coffee grinders vary widely in their ability to consistently grind the coffee at different levels of coarseness. They can range from very coarse (similar to raw sugar), to medium (similar to table salt or granulated sugar), to fine (powdery with a hint of grittiness).
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.
Blade Coffee Grinders
The blade type coffee grinders are the most inexpensive on the market. They are suitable if you are just looking to make a quick cup of coffee and nothing more. A benefit is that it's extremely easy to use and cleanup is a snap.
There are some downfalls however. When using a blade grinder, your grounds may be inconsistent and size and the heat of the blade and actually make the grounds may become bitter. The blade grinders, because of their chopping method, also cannot achieve the consistency needed for espresso. Even the coarse and medium grinds vary widely and are not consistent at all.
Burr Grinders (Flat Wheel)
If you are a coffee connoisseur and can appreciate the fine aroma and savoring flavors of each cup, putting a little extra money into a good grinder is worth it. Going with a burr grinder is a great way to start. Flat wheel burr grinders are the preferred method of grinding coffee. They work by crushing the beans between one spinning and one stationary, rigid disk.
The disks spin more slowly than a blade grinder which generates less friction and creates a much more consistent grind. The disadvantages are that they must be cleaned (which requires a little work) especially if you don't use it on a regular basis.
The beans which are gravity fed from a hopper, can also get stuck pretty often and need to be stirred to get them to flow into the disks again.
Burr Grinders (Conical)
Conical burr grinders are some of the best on the market. The advantages of the conical versus the flat wheel are that they have the most consistent grind. They also spin even slower creating less friction and less static electricity which causes the coffee to stick in the crevices of the grinder making it harder to clean.
In addition the beans, at least in my experience, clog up much less in the hopper.
The disadvantages are that they tend to be the most expensive because of the cost to manufacture the grinding cones.