Why a burr grinder?
As mentioned above, the blade variant of coffee grinders allow 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 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.
