the grinder on my bes876 is making a horrible screeching or grinding metal noise, what's broken?

Diagnosis

The screeching or metallic grinding noise in the Breville Barista Express Impress BES876BSS is almost always caused by a foreign object becoming lodged between the upper burr and the lower conical burr. While coffee beans are organic, "quakers" (under-ripe beans) or small stones occasionally sneak through the roasting process. Because the BES876 uses a high-torque motor to drive the burrs, a hard object doesn't always jam the motor immediately; instead, it gets crushed or wedged, creating a high-pitched friction sound as the metal burrs scrape against the debris or, in worst-case scenarios, against each other. Another possibility is "burr migration" or a loose upper burr assembly. If the locking mechanism on the upper burr has vibrated loose, the burr can shift off-axis, causing the cutting edges to collide. You can confirm this by turning the machine off and attempting to rotate the upper burr by hand (after removing the hopper); if it feels loose or wobbles, the assembly is compromised. However, if the burr feels secure and the noise started suddenly during a grind, you are dealing with a foreign object obstruction.

How to Fix It

To clear the obstruction and restore the grinder, follow these precise steps:

1. Power down the machine and unplug it from the wall outlet to prevent accidental activation.
2. Remove the bean hopper by twisting it to the unlock position and lifting it straight up. Ensure all remaining beans are vacuumed out of the chamber.
3. Locate the grind size dial on the left side of the machine. Rotate the dial to the coarsest setting (the highest number). This opens the gap between the burrs, providing more room to dislodge the debris.
4. Remove the upper burr. Grasp the wire handle of the upper burr and rotate it counter-clockwise until it releases. Lift it out of the housing.
5. Inspect the lower conical burr. Use a flashlight to look for small pebbles, pieces of hard plastic, or metallic fragments. Use the provided cleaning brush or a vacuum with a narrow nozzle to suck out all debris from the crevices of the lower burr.
6. Clean the upper burr surfaces using a dry microfiber cloth. Do not use water, as this will cause the burrs to oxidize and rust.
7. Reinsert the upper burr, ensuring it seats perfectly flush. Rotate it clockwise to lock it back into place.
8. Replace the hopper and run the grinder for 2 seconds without beans to verify the noise has ceased.

If That Didn't Work

• Perform a Deep Burr Degrease: If the noise is more of a "strained" hum than a screech, you may have a buildup of coffee oils and fines that have hardened into a cement-like paste. Use a specialized grinder cleaning tablet (like Urnex Grindz). Run these through the grinder in 3-4 small batches to scrub the metal surfaces and remove stubborn residue.
• Check the Drive Socket: If the noise persists and sounds like slipping, the drive socket (the part that connects the motor to the burr) may be stripped. Remove the upper burr and inspect the teeth of the drive gear. If the metal teeth are rounded off, the burr will slip and screech. This requires replacing the upper burr assembly (Part #BES876-BURR).
• Inspect the Capacitor: If the motor sounds like it is struggling to turn (a low-frequency grind), the start capacitor may be failing. This is an internal electrical failure and requires a technician to replace the capacitor on the main PCB.
• Replace the Burrs Entirely: If you find visible gouges or "chips" in the metal of the burrs after removing a stone, the burrs are permanently damaged. Even if the noise stops, your grind consistency will be ruined. Replace both the upper and lower conical burrs to restore factory specifications.

Heads Up

• Avoid Oily Beans: Dark-roasted, oil-coated beans clog the BES876's internal chutes faster and can lead to "clumping" that puts unnecessary strain on the motor.
• Never Use Water: Never use water or liquid cleaners on the burrs. The stainless steel is treated, but moisture will lead to corrosion, which creates a gritty, metallic taste in your espresso.
• Regular Vacuuming: Every 30 days, remove the hopper and vacuum out the "dead space" around the burrs. Accumulated fines can compress and create friction that mimics the sound of a mechanical failure.
• Avoid "Pre-Ground" in Hopper: Never put pre-ground coffee into the hopper; it will immediately jam the burrs and potentially burn out the motor.