A coffee grinder that drifts, meaning shots run faster or slower though the setting has not changed, usually has worn burrs, a buildup of old grounds and oil, a loose or worn adjustment collar, or a motor that slows as it heats. Humidity and temperature in the shop can add to it. The first steps are to clean the grinder, check the burrs for wear, and confirm the adjustment holds. If drift continues, a technician can measure burr wear and motor speed.
Baristas often compensate for drift by changing the grind several times a day. That works, but it hides a problem that will get worse, and it wastes coffee while you find the right setting each time. A grinder that holds its setting makes every other part of the espresso routine easier.
Causes of drift and how to spot them
| Cause | What you notice | What helps |
|---|---|---|
| Worn burrs | Shots run fast, need finer settings over time, uneven particle size | Replace burrs per maker interval |
| Oily grounds buildup | Clumping, retention, flavor off, inconsistent dose | Clean burrs and chute; use grinder cleaning tablets as the maker allows |
| Loose or worn adjustment ring | Setting moves on its own, dial feels loose | Technician inspection or replacement of collar or stops |
| Motor slowing when hot | Early shots fine, later shots slower to grind | Check ventilation, load and motor condition |
| Humidity and room temperature | Shots change between morning and afternoon | Adjust routine; keep beans sealed |
| Doser or timer drift | Dose weight varies | Recalibrate or service the timer and sensor |
Burr wear is the most common cause
Burrs dull gradually. A dull burr crushes beans rather than cutting them, which creates more fines and uneven particles. The result is shots that run inconsistently, taste muddy and need constant adjustment. Burr life depends on the burr material and the volume you grind. A busy cafe may need new burrs far more often than an office machine. Makers publish a rough interval in pounds or hours; use it as a guide and trust the coffee in your cup over any number.
Replace burrs as a pair, and calibrate after installing them. New burrs need a new reference point for the grind setting, and many grinders have a zero or touch point that must be set correctly. Set it wrongly and burrs can touch, which damages them quickly.
Cleaning matters
Old coffee oil builds up on the burrs, in the grinding chamber and in the exit chute, where it holds grounds and releases them unevenly. This causes clumping, a changing dose, and sometimes a rancid taste. Wipe and brush the chamber daily, and deep clean on a schedule. If you use grinder cleaning tablets, use only the kind the maker approves. Unplug the grinder before you remove the hopper or reach into the burr area.
Safety and electrical notes
Never put fingers into the grinding chamber with the grinder plugged in. If you hear metal scraping, which may mean a foreign object such as a small stone or a bolt, switch the grinder off at once and unplug it. If the motor hums without turning, smells hot, or trips a breaker, stop using it. Forcing it can burn out the motor and wreck the burrs.
What a technician measures
- Burr wear and alignment, and whether the burrs are parallel and clean.
- Motor speed and current draw, both cold and after extended use.
- Adjustment mechanism for play, looseness or worn threads.
- Doser, timer or sensor accuracy on dose-by-time and dose-by-weight models.
- Chute, hopper and bearings for wear and coffee oil buildup.
Replacing burrs and fixing an adjustment ring are typical repairs and are usually moderate in cost compared with replacing a grinder. A failing motor or damaged burr carrier costs more. We quote in writing and tell you plainly which repairs are worth making on your particular grinder.
Keeping the grind steady
- Brush the chamber and chute at the end of each day.
- Keep beans in a sealed container away from sun and heat.
- Do not fill the hopper for the week; use what you need for one or two days.
- Keep a small log of grind settings and shot times.
- Schedule burr replacement before shots become unpredictable.
We repair on-demand and bulk grinders for cafes, restaurants and shops in Miami, Los Angeles, Houston, New York and San Diego. We are an independent repair company, not affiliated with any maker. Same-day appointments are often available, and our work carries a 30-day warranty.
FAQ
How often should burrs be replaced?
It depends on volume and burr type. Follow the maker’s interval as a starting point and replace sooner if shot quality drops or you need to adjust constantly.
Why do my shots run faster in the afternoon?
Heat, humidity and the motor warming up can all change particle size and flow. Cleaning, ventilation and fresh beans help.
Can I clean burrs with rice?
Many makers advise against it because rice can scratch the burrs or leave residue. Use grinder cleaning tablets approved for your model.
Is clumping a sign of a bad grinder?
Often it is oil buildup, static or humid beans rather than a failed grinder. Clean it thoroughly first; if clumping continues, have the burrs checked.