If your Breville built-in grinder hums but no grounds come out, the burr chamber or the outlet chute is clogged. Fix it in two passes: run the grinder empty and brush the burrs, and if that fails, pull the lower burr and clear the chute. Breville lays out both procedures in the Barista Express BES870 instruction book (pages 25 to 26).
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Why it jams in the first place
A jammed grinder almost always means one of two things. Either you set the grind too fine and the burrs bound up trying to force beans through, or oil and fines packed into the chute until nothing could pass. Oily dark roasts are the usual culprit because the surface oil turns coffee dust into a paste that sticks to metal. The tell is sound: the motor hums or strains but the burrs will not turn, and the outlet stays dry.
Before you take anything apart, rule out the easy stuff. Make sure the hopper is seated and locked, because the grinder will not run if the hopper is not in position. Check that you did not leave the grind size at 1 or 2 with a stale, oily bean. If the burrs are simply coated rather than blocked, the standard cleaning cycle below is all you need.
Two clearing procedures, from the BES870 manual
Breville separates routine burr cleaning from unblocking the chute. Start with the first. Only move to the second if grounds still will not exit after the burrs are clean. Both are quoted from the BES870 instruction book. The burrs are extremely sharp, so handle them by the plastic housing, not the cutting edges.
| Procedure | Steps (BES870 manual) | Tools |
|---|---|---|
| Standard grinder cleaning (page 25) | Unlock and empty the hopper, replace and lock it, run the grinder empty to clear beans, then unlock and remove the hopper. Unlock and remove the top burr. Clean the top burr, lower burr, and chute with the supplied brush. | Cleaning brush (in the box) |
| Advanced cleaning, blocked chute (page 26) | Remove the hopper, set GRIND SIZE to 1 (finest), use a 10mm socket and rotate clockwise to loosen the nut only. Set GRIND SIZE to 16 (coarsest), unlock and remove the top burr. Remove nut, spring and flat washer, then carefully remove the lower burr. Remove the grind fan and washers with long-nose pliers. Unblock the grinds exit chute with the brush or a pipe cleaner. Reassemble in reverse, rotate the nut counter-clockwise to tighten, set GRIND SIZE to 5, replace and lock the hopper. | 10mm socket, long-nose pliers, brush or pipe cleaner |
The order matters on reassembly. The manual is specific: when you drop the lower burr back in, align the drive pin with the cavity, then seat the flat washer and spring washer before you tighten the nut. Skip the alignment and the burr will not sit flat, which sends you right back to a grind that binds.
One detail that trips people up: on the advanced pass you loosen the nut clockwise, not the usual counter-clockwise. Breville reverses it because the grinder shaft spins the other way. Follow the printed direction and use the 10mm socket, not pliers, so you do not round the nut.
Keep it from happening again
Brush the top burr weekly rather than waiting for a clog. Pull the hopper, lift the top burr out, and clear the loose dust with the supplied brush. Keep the hopper no more than half full so the bean feed stays steady, and buy oily dark roasts in smaller amounts so they do not sit and go greasy in the chamber. If you grind espresso fine every day, a monthly chute check with the pipe cleaner keeps the outlet open. Replacement burrs, brushes, and burr-cleaning tablets are easy to find if yours are worn or missing.
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FAQ
Why does my Breville grinder hum but not grind? The burrs are bound or the outlet chute is packed. Run the grinder empty and brush the burrs first; if grounds still do not come out, do the advanced cleaning to pull the lower burr and clear the chute with a pipe cleaner.
What tool do I need to remove the lower burr? A 10mm socket to loosen the retaining nut, plus long-nose pliers to lift out the grind fan and washers. Breville has you set the grind to 1 to loosen and 16 to remove, per the BES870 manual.
How do I stop the grinder jamming again? Brush the top burr weekly, keep the hopper half full, and avoid grinding very oily dark roasts too fine. Oil and fines are what pack the chute.