Coffee and Caffeine FAQ

Any grinder is better than having your coffee preground at the store. Pregrinding is just a way of insuring stale coffee.
Perhaps the earliest form of grinding anything, whether it be spices or coffee, was the simple mortar and pestle approach. The item to be ground - or crushed as it were - was placed in the bottom of a bowl, and the blunt end of a stick was used to crush said item along the bowl's bottom and sides. Following this - and history tends to lead us down numerous paths - mechanical means replaced the mortar and pestle. Manually operated, the coffee (or, again, spice, wheat, corn... whatever) was placed between a stationary and a moving disc. The movement of the one disc atop the other created a grinding force. This is also known as milling; a term we carry into the present.
Milling has become very efficient with the use of electrical motors as opposed to horses, water, steam, or human-power. And milling, as a process, is as common to the agricultural industry as it is to coffee. To understand the benefit of milling coffee, let us first compare it to another popular grinding technique, the blade-style coffee grinder. Available in practically every house wares store in the world, the blade-style grinder uses a small, universal electrical motor to spin two metal blades at very high speeds. When in contact with the coffee beans, the blades chop and crush the bean's structure. Akin to the mortar and pestle for not creating a uniform grind, this method is quick and inexpensive. Many models of this type can be had for less than 20$US.
A step up, and the primary focus of this article, is the burr style, or milling style coffee grinder. Like the wheat or corn grinder, and essentially identical to commercial, industrial-sized grinders, the burr grinder for today's consumer is available in a myriad of colors, features, materials, and prices.
Why a burr grinder?
As mentioned above, the blade variant of coffee grinders allows a varying particle size from the resultant grind. The leading reason for the use of a burr grinder is the ability to produce a uniform grind of the beans. A uniform grind is important for a few different reasons. First, it provides an even surface area for extraction during whatever brew process you may wish to use. Second, for espresso, the uniform grind allows for even wetting and even packing of the grounds.
How come?
Let us return above. An even grind will provide for an even extraction of the oils from the coffee. Ill-proportioned grind will cause some of the coffee to over-extract, and some to under-extract. Over-extracted coffee will taste bitter and overly pungent. Under-extracted will taste weak and thin.
Burr grinders, ideally and theoretically, pass an incoming bean under (or in between) its burrs once. Whether it be for one revolution or two, the bean, as it finishes its pass, is completely crushed into identically-sized pieces. Blade-style and mortar and pestle re-grind the coffee, which provides the inconsistency mentioned above.
The Big Debate - Flat-Plate Burr Grinders vs. Conical Burr Grinders:
Burr grinders are distinct by two forms. The first style has the burrs that are plate-shaped and lie atop each other. In the second model, the burrs are shaped like two mating cones; the grinding teeth facing toward each burr set. The debate lies with life expectancy of the burrs, grind consistency, and ease of cleaning. To begin with, both variations are easy to clean so long as the manufacturer designed the grinder to allow one of the two burr sets to be removed. To my knowledge, every manufacturer has done so. It is up to the owner to find the appropriate cleaning tool used to get into the teeth's grooves. Incidentally, a stiff bristled brush like that of a toothbrush works well. The debate flourishes here: does a conical burr-set wear more but provide a greater grind consistency and slower operating speed (due to prolonged contact between bean and burr), or does the flat-plate burr-set provide greater consistency and life because of its ability to operate at faster speeds? You decide. There are arguments for and against both parties. All in all, to the average consumer, this argument is like the blowing of the wind. Meaningless.
"You get what you paid for."
I mentioned this above. And it is true, especially when you figure in other factors to your potential purchase. These factors are as follows:
Does the machine come with a warranty? If so, how many years?
May I try the machine first before committing to a purchase?
Is the machine too loud?
Is the machine easy to clean up? Does its spill or throw ground coffee all over the place?
Is there service available in my area? If so, how much extra and how easy is it to obtain?
Is the machine repairable by myself or a local appliance repairperson?
Keep all of these questions in mind when and after you go shopping. You'll find distinct differences between each and every model mentioned above. It is true that the higher you go, the greater the quality of the machine - both in materials used and end product. Consistency is still very much a driving argument and consistency is best achieved when higher-quality components and material are used.
These are the biggest questions you need to keep on your mind:
How much will you use this grinder and for what reasons? Do you plan on only grinding for one style of coffee? Do you plan on using it daily? Do you plan on using many different types of coffee beans?
If you can answer these questions, you can narrow down your search very easily.
Another point that deserves attention is that many cheap coffee grinders have a tendency to have some type of static problems. Some of the more expensive models can also have these same problems so, as with other considerations, be sure to try the grinder before you buy.
There are now low cost burr grinders that have hit the market. They can be had for as little as $20. If you are looking for an economy grinder for drip pot coffee you may want to give one of these some thought. One thing you should know about these low cost grinders is that they typically use plastic burrs so they will not hold up as long as a grinder that use steel burrs.

My admittedly biased personal recommendations:
I'm very happy with my Baratza Maestro. I have had it for several years and it works very well for any type of coffee grinding. It does a decent job of espresso but for a good espresso machine I'd recommend something a little higher end. The Baratza Maestro Plus gets fair reviews for an espresso grinder on a budget. The Mazzer Mini and Rancilio Rocky have been the standard in espresso for a long time. I would probably stay away from blade grinders for coffee unless budget is your main consideration.