The coffee-making process consists of moving water through the ground coffee, you should pay close attention to those two items. Regardless of how much money you spend on an espresso machine, using improperly ground coffee and/or bad-tasting water will produce lousy-tasting coffee. It would be a true statement to say that the coffee grinder is probably the most important piece of coffee equipment you have.
A grinder’s sole function is to produce consistently sized grounds. Without that consistently sized ground, your high-dollar coffee machine will never make a great cup. There are numerous, quality commercial and home grinders that produce great coffee grounds. However, you won’t find a good, new, commercial grinder for $150 or a good, new, home grinder for $25. The price for a good commercial coffee grinder starts easily at the $1000 range and goes up. Burr grinders are the key to a good grind for espresso drinks. Blade grinders chop the bean into inconsistent sizes – and although not ideal, can be used for cold brew, French press and other immersion methods. Burr grinders can be calibrated to grind consistently and the size of the grind can be easily adjusted.
Once you’ve adjusted your quality grinder to produce the grounds that best suit your coffee, don’t assume that setting will never change. You will find that humidity effects your espresso shot time. Higher humidity usually requires a little finer grind, while lower humidity may require a slightly coarser grind.
The grinder burrs are what actually cut the bean and they have a finite lifespan; as the burrs wear, you must adjust the grind setting to maintain the same grind. Depending upon several variables [cutting area (i.e. 58mm, 63mm, 71mm), shape (flat or conical), and the manufacturing material (steel or ceramic)], burrs will grind anywhere from 600 to 40,000 lbs of beans before requiring replacement. Check the manufacturer’s literature to find your model’s burr rating.
Manufacturer’s recommended burr ratings for some of the more popular commercial grinders: