Grinding generates heat through friction, and how much it matters depends entirely on volume.
What happens at home
An 18 g (0.6 oz) dose takes 8 to 12 seconds. The burrs warm slightly and the grounds leave at close to room temperature.
Measured temperature rises of a few degrees are typical. That is not enough to drive off aromatics meaningfully.
For a home user, this is not a real problem.
Where it does matter
Commercial grinders running continuously. Burrs reach genuinely high temperatures over a busy service, and the last dose of a rush behaves differently from the first.
This is why commercial grinders have large burrs — more mass, more surface, better heat dissipation — and why some have cooling fans.
Very large flat burrs at home, ground back to back, can warm up over several consecutive doses.
The secondary effect
Heat changes grind behavior more than it changes flavor. Warm burrs sit at a marginally different effective gap, so shot times can drift over a session.
If shots creep faster after four in a row, this is a plausible cause.
What actually causes stale-tasting grounds
Retention, not heat. Grounds left in the chamber overnight are stale by morning.
Grinding ahead of time. Ground coffee degrades in minutes.
The practical answer
Do not worry about grinder heat at home. Do worry about retention and about grinding immediately before brewing.
What people want to know
Do conical burrs run cooler than flat burrs?
Conical burrs turn more slowly in many designs and shed heat well, but at home neither gets hot enough to change the taste. Burr size and grinding volume matter more than shape.
Last reviewed 30 October 2026