A grinder that stalls or refuses to turn has a short list of causes.
A foreign object
A stone. Coffee is a dried agricultural product and stones do get through, particularly in commodity coffee.
The grinder will stall hard and may have chipped a burr. Open it, remove the object, and inspect the burrs.
This is the main cause of catastrophic grinder damage.
Adjusted too fine with beans in the burrs
Many grinders must be adjusted while running. Turning the collar finer with beans wedged between static burrs jams them and can strip the adjustment thread.
Check the manual. It will say, and it is the commonest self-inflicted failure.
Oily beans
Dark, oily roasts pack the chute into a solid mass. The burrs turn and nothing comes out, then the motor labors.
Clean it, and consider a drier roast.
Overfilling
Some grinders choke if the hopper is packed and the throat cannot feed.
Moisture
Genuinely wet beans — not RDT, but beans stored damp — will paste up in the chamber.
What to do
Unplug it. Then disassemble as far as the manual allows, remove the obstruction, brush everything, and reassemble.
Do not force the motor by repeated switching. Thermal cut-outs exist on better grinders; on cheaper ones the motor burns out.
Prevention
Buy hand-sorted specialty coffee, adjust while running, and clean monthly.
Last reviewed 30 October 2026