Sound familiar?
Your grounds look coarse no matter the setting, shots gush, or you keep having to grind finer. The dial feels stiff when you move from coarse back to fine. Your zero point seems to have moved.
What is happening
This is called false chirp, and it is a normal occurrence in high-precision flat burr grinders. Tiny coffee particles get packed into the flat finishing areas of the burrs. Coffee rubbing on metal sounds like the true burr chirp you use to set zero. If you zeroed on that sound, the grinder is actually coarser than the dial shows. Burrs with large finishing flats, like SSP HU, SSP CV3, and Mazzer, are the most prone to it.
Video:
How to clear it
- Turn the grinder ON. Adjust only while it is running.
- Slowly turn the dial finer. You will feel some resistance, which is normal with the grinder running, as it pushes the compacted grounds through.
- Stop as soon as you hear true chirp, a sharp metal-on-metal sound.
- Turn the grinder OFF and rezero (see Setting the Zero Point on Your Z1).
If the dial feels very heavy, do not force it. Clean the burrs and chamber instead (see Opening, Cleaning, and Closing Your Z1).
Keep it from coming back
Grind espresso first, then move coarser for pour over, rather than sweeping from coarse back to fine. Tap the top of the open funnel after grinding. If you own two burr sets, keep your espresso set for espresso and use the other for filter.
Zero point shift
A small shift after cleaning, burr swaps, or while new burrs season is normal. A 20 to 50µm change looks big on the dial, but a human hair is about 100µm thick. If the zero keeps shifting after about 5kg of coffee:
- Rule out false chirp using the steps above.
- Turn the grinder OFF and unplug it.
- Open the grinder and remove the burrs.
- Clean and carefully reseat the burrs, then reassemble with the dial at about 100µm.
- Reset the zero point.
Still having trouble? Email info@zerno.co with a short video.