Blade Grinder
The least expensive type of coffee grinder is the blade grinder, which often looks like a little spice grinder. It operates by cutting beans with a blade, similar to how a small food processor might. A blade grinder’s disadvantage is that it produces coffee particles of variable size. Some will be big, some will be small. If you want to grind beans to a medium or coarse texture, some particles will always become fine and powdery. When the coffee particles are all different sizes, the extraction rates vary, resulting in a cup with an inconsistent flavour. Furthermore, the blade’s contact at high speed generates heat, which might harm the beans’ flavour. Blade grinders are simple, cheap and very convenient. Many people use them as a secondary grinder. Many people have an expresso machine and a burr grinder at home but use a French press and a blade grinder at work or when they are travelling or on holidays. With practice, blade grinders can make a perfectly good cup of coffee using a French press or a stovetop Moka Pot.
Don’t forget; any grinder is better than no grinder. Sometimes you’ll get a little grit in the bottom of your cup from excess “fines” but the boost in flavour you get from using freshly ground beans is a good trade-off for a little residue in your cup.
Burr Grinder
Instead of using blades to chop the beans, a burr grinder (also known as a burr mill) crushes them between two rough discs known as burrs. Because the particle size is determined by the distance between the burrs, this approach gives a more consistent grind. There are three types of burr grinders, the old-fashioned manual grinder (which looks like a hand-cranked pepper mill), the electric flat burr grinder (more adjustable; popular for commercial usage), and the electric conical burr grinder (quieter; popular for home use). Nearly all burr grinders are more expensive than blade grinders but the fact is that in most instances, they are worth the extra cost. Being able to control the grind size will give you more options on how you make your coffee and will allow you to experiment more with different coffees and different methods.