The Blade Grinder
The blade grinder is often cylindrical in shape. The top usually will have a removable cap that covers a recess with propeller like blades, similar to a blender or food processor. In most cases there is a button on the cap or side of the grinder you press in to start the blades spinning. The spinning blades chop the bean repeatedly leaving you in control of the exact grind you're left with. This style of grinder makes it very difficult to achieve consistent grind size. Also the spinning blades can cause the ground coffee to heat causing the taste of your brewed coffee to be different than normal. A burr grinder is the preferred method for consistent grinding. In a pinch a blade grinder will do, as it's better for coffee flavor than having pre-ground coffee. A blade grinder can be found for as little as $10.