How to Adjust Espresso Dosing Grinders and Key Considerations for Coffee Grind Size Settings

Understanding Dosing Grinders: Are They Really Convenient?

Dosing grinders, as the name suggests, are coffee grinders that can set the amount of coffee grounds for a single grind, eliminating the step (and time) of weighing the powder. At first glance, they seem like a more convenient type of grinder.

But is this really the case? Dosing grinders operate in two ways—by weight and by time. Most dosing grinders on the market use the time-based method. Taking the grinder used by FrontStreet Coffee as an example, you can set the grinding time to stop automatically. For instance, if grinding 20g of coffee requires 3.5 seconds, you can set the grinding time to 3.5 seconds, and the grinder will grind for 3.5 seconds in subsequent dosing operations.

While this might seem straightforward, FrontStreet Coffee has found that the grinding error can range from 0.3g to as much as 1.3g in actual use. There are several important details to consider.

Detail 1: Gaps Between Coffee Beans

Looking at the densely packed coffee beans in the hopper, there are actually significant gaps between individual beans. This involves the principle of accumulation. If spheres of equal size were arranged at equal distances, the gaps between them would be uniform. However, coffee beans are irregular objects of varying sizes. This means the space between beans differs, causing slight errors (±0.3g) during timed grinding.

Detail 2: Bean Quantity in the Hopper

The amount of beans in the hopper is an often-overlooked factor. Typically, people fill the hopper completely and only refill it when it's empty. FrontStreet Coffee conducted an experiment comparing timed grinding with a full hopper versus a 1/5 full hopper, keeping all other parameters constant. Using 3.5 seconds to produce 20g of grounds with a full hopper as the baseline, the same 3.5 seconds with a 1/5 full hopper produced only 18.7g—an error of 1.3g. Therefore, in frequent daily brewing, blindly trusting the dosing function could result in decreasing output as the amount of beans diminishes. This is why FrontStreet Coffee, despite using a dosing grinder, still uses an electronic scale to verify that the required amount is achieved.

This occurs because when the hopper is full, the weight of the upper beans creates pressure that pushes the lower beans through the burrs. As the bean quantity decreases, this pressure also diminishes. When the hopper is nearly empty, you might even notice "jumping beans" (coffee beans being bounced upward).

Therefore, FrontStreet Coffee also recommends maintaining the hopper at 40-70% capacity (don't wait until it's completely empty to refill), as this state provides more consistent results.

Detail 3: Residual Coffee in the Grinding Channel

If you notice that your dosing grinder sometimes produces more and sometimes less grounds, it might be due to coffee getting stuck in the grinding channel. If the channel can be dismantled, regular cleaning will reduce the occurrence of such situations.

Detail 4: Changes in Grind Setting

Changing the grind setting will also affect the output in timed grinding. When the grind setting is adjusted finer, the amount of grounds produced in the same time will decrease; when adjusted coarser, the output will increase. Therefore, after adjusting the grind, you need to reset the time.

Finally, to achieve consistent results, even with a dosing grinder, it's still advisable to use an electronic scale for verification.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473