As you begin to research grinders, to find the one that best fits your needs, you may come across ones that operate at different RPMs. What does this mean to you? Is it just another thing designed to make the research harder for the machine you’re dying to have on your counter, or just make things more complicated? Well, it’s actually something in between.
First, RPM, if you didn’t know, stands for Revolutions Per Minute. Basically, it’s how many times in a minute the burrs rotate. This can be good and bad, as there are pros and cons of each.
The Low Speed Grinder
Low speed or high RPM grinders are usually lower cost grinders in the $200 or less range. They have lower RPMs for a couple of reasons. Usually they have smaller motors, and use gear reduction to step down to the smaller RPM. They also usually have smaller burrs, and most are conical shaped. The lower RPM grinders usually have less heat buildup. With the gear reduction system, however, there is likely more of a chance of static buildup. And with the smaller burr set, consistency is not usually ideal for espresso machines. Examples of these would be the Baratza Maestro, Virtuoso, and Capresso Infinity.
These machines work well with pressurized baskets, or for brew processes that don’t require consistent grinds, like French press, drip, etc.
The High Speed Grinder
Usually high speed grinders are also high end in price and performance. They usually have flat burr sets, and beefier motors. The flat burrs provide a more consistent grind with more surface area to grind with, and the higher RPMs grind the beans faster and give it less time for heat to be transferred: it’s processed through the grinder before it gets affected by any grind friction.
Also, hi-speed grinders are direct drive, and that means less gears to wear or break, and gives a quieter grind. Examples would be the Rancilio Rocky, Mazzer Mini, and Compak grinders.