Eureka mignon grinders are popular for a reason. They are of good quality, they are quiet, they look nice and they are reasonably priced. They however have a very evident flaw: the grind size adjustment dial is too small, too sensitive, too imprecise. Once you touch it, good luck going back to its previous setting. It makes it impossible to switch between different roasts and brew methods in a consistent way. Overall it makes for a very frustrating experience and I think it ruins what otherwise is a perfectly capable grinder.
Luckily the problem is easy to fix and third party makers have come to the rescue, selling alternative grind adjustment dials, such as this 3D-printed one from finecoar or this aluminium one from ARO Espresso. This fix applies to pretty much the whole Mignon line, such as the popular base model Silenzio and the more expensive Specialità , with the exception of the Perfetto. This is because the adjustment knob can normally be removed by just unscrewing it fully, and the replacement one can then just be screwed in on the same rod.
two types of knobs
The way the (base) grind size adjustment works is very simple:
- the knob rests on the metal frame of the grinder and screws onto the adjustment rod,
- the rod is directly connected to the motor and lower burr assembly, which is allowed to slide vertically,
- tightening the knob pulls onto the rod, making the motor assembly to slide upwards and therefore reducing the gap with the upper burr, which is fixed onto the frame.
The Perfetto however has the so called “Easy Setting System”: it consists of a different knob that goes through the whole range of grind sizes in one single rotation (instead of the three of the normal knob) and has generic indications of what sizes are appropriate for different brew methods. The sensitivity of this knob makes it even more difficult to set the grinder properly, making it basically unusable for espresso.
According to all information I was able to find, this ESS knob is supposedly not removable. I even sent an email to Eureka’s customer service, explaining that I wanted to replace the knob with a standard one, and they confirmed that it is not removable.
Luckily, this is false. And now we are going to see how to remove it.
Using a thin flat screwdriver, with a bit of caution, it is possible to lift the top plastic cap of the ESS knob and remove it. Setting the grinder as tight as possible, i.e. to its 0 setting, helps as it raises the top cap with respect to the knob’s side and makes it easier to insert the tool underneath to lift it.
This is what we see next:
By turning the knob we can already see how it works:
- the central brass piece is tightly screwed onto the adjustment rod and it does not turn,
- the outer plastic part of the knob rests onto the frame and, by turning it, pulls the central brass piece up, and with it the rod is also pulled.
Looking inside the central, threaded, hole of the center piece we can see that there is a little screw with a small hexagonal head. This is used to set the 0 point of the dial. We can loosen it to help in the process.
Now we need to take some long nose pliers that fit in the two smaller holes and carefully start unscrewing the brass piece from the adjustment rod. This requires some force and the rod will twist slightly. A very small drop of WD-40 or any other penetrating oil on the threads can help, but we need to be careful that it does not contaminate any area that will be in contact with the coffee.
Once the brass piece is completely removed from the rod, we can also just slide the outer plastic part off it. Now let’s just take the new knob we bought, put a bit of silicone grease in its threads and screw it in-place.
Congratulations, you have successfully replaced the “unreplaceable” knob of the Perfetto. Now you can have fun with it.