Coffee Equipment Reviews

Troubleshoot · Grinders

Grinder burrs scraping each other — alignment and shimming

By Andres Borrero Updated

A grinder makes a metallic scraping or grinding noise during operation — either continuously or intermittently — even when empty of beans.

Diagnostic checklist

Run through these before opening anything — half of all "broken machine" reports resolve at one of these steps.

  1. At what grind setting does the scrape happen? If only at very fine settings, the burrs are simply too close — coarsen up.
  2. Empty the grinder and run it dry. Does the scrape continue without beans? If yes, alignment issue. If no, the issue is between burrs and beans (popcorning or bean fragments).
  3. Has the grinder been dropped recently? Drops can misalign or chip burrs.
  4. When were the burrs last cleaned? Buildup in the burr threads can shift the zero point.
  5. Open the burr chamber and inspect: are the burr edges chipped, dented, or visibly warped? Visible damage = replace, not realign.

Possible causes and fixes

Ordered by probability based on community-reported frequency. Try the first cause first.

#1 Over-fine grind setting (most common)

Most grinders use a threaded adjustment ring that moves the burrs closer together at finer settings. At the absolute finest setting (or below the user-accessible zero), the burrs physically touch. Some grinders allow this; most do not and the scrape is the warning.

Fix

Coarsen the grind setting by 2-3 steps. If the scrape stops, you were simply past the safe limit. Many grinders ship with a "calibration" or "zero" procedure documented in the manual — recalibrate the zero point so the user-visible "1" setting is just above touching, not below.

#2 Burr buildup shifting the alignment

Coffee oils and very fine particles can build up in the burr threads, on the burr-mounting surfaces, or in the alignment housing. This effectively raises the burr a fraction of a millimeter — the "zero" shifts and the user-visible scale no longer matches the real burr position. Result: a setting that worked last month now scrapes.

Fix

Remove the burrs (most grinders have an access cover). Clean both burr surfaces and the mounting cup thoroughly — use a soft brush, then a microfiber. Wipe the alignment threads. Reinstall, recalibrate the zero. The scrape should disappear.

#3 Burr alignment off-axis (requires shimming)

Some grinders ship with the upper or lower burr slightly tilted relative to the rotation axis — not enough to scrape at most settings, but enough to scrape at fine settings on one side. This is a manufacturing tolerance issue, most common on lower-tier grinders ($150-400 range).

Fix

Shimming. Place a thin shim (paper, plastic foil, dedicated alignment shim) under the high side of the burr to tilt it back to true. The home-barista community has extensive shimming guides for popular grinders (Eureka, DF64). This is intermediate DIY — comfortable with mechanical adjustment. If unsure, contact the manufacturer; some will exchange under warranty if alignment is significantly off.

#4 Damaged burrs (after a drop or foreign object)

A stone or piece of debris in the beans can chip a burr edge. A chipped burr makes a distinct "clack-clack" sound at every rotation, not a continuous scrape. Dropped grinders can also bend the burr mount.

Fix

Inspect the burrs visibly. Chips or dents = replace. Most grinder manufacturers sell replacement burr sets for $30-80. Aftermarket burrs (SSP for premium grinders) cost more but can be an upgrade rather than just a fix.

When to stop DIY and call service

If the grinder is under warranty: contact the manufacturer first. Persistent burr scrape on a new grinder is almost always a warranty case — they will either send replacement burrs, calibration shims, or RMA the unit. Shimming is a real and accepted fix for some manufacturing tolerances, but a new grinder should not require the user to shim it. For out-of-warranty grinders, basic shimming is DIY-friendly with online guides; replacement burrs are 15-30 minute installs.

Replacement parts and supplies

  • Replacement burr set (manufacturer-specific)

    OEM burrs from the grinder maker — $30-80 typically. For an upgrade rather than fix, SSP or other aftermarket burrs (espresso-optimized geometries) cost $100-200 and require specific compatibility.

  • Alignment shims (per-grinder, often included free from manufacturer)

    Many manufacturers will ship shims under warranty. Aftermarket shim kits exist for DF64, Eureka, and other popular grinders for $5-15.

Frequently Asked Questions

Is some burr noise normal during grinding?

Yes — burrs cutting beans make a distinct crunching/whirring sound. What is NOT normal is a metallic "scraping" or "shrieking" sound that continues with no beans in the chamber. The difference is roughly: the normal sound varies with beans; the scrape sound is constant.

My new grinder scrapes only at the finest setting — defective?

Possibly, possibly not. Many grinders document that the "1" setting is below the safe minimum and intended only for manual recalibration. Check your manual. If the manual says "1" should be usable for espresso and your grinder scrapes there, contact the manufacturer.

Do I need a feeler gauge to align burrs?

Not for the basic check — you can verify alignment by hand-rotating the burrs slowly with the grinder unplugged and feeling for binding. For precision shimming on espresso grinders, a feeler gauge or printed paper shim guide is helpful. $10 on Amazon.

After fixing alignment, do I need to re-season the burrs?

Usually not — seasoning is for breaking in new burr edges, not for restoring alignment. After fixing alignment, the existing burrs (assuming undamaged) should perform as before within a few doses.

Last reviewed: . We update troubleshoot guides when the manufacturer publishes new service documentation, when a recurring failure pattern shifts in the community, or when a fix becomes obsolete (e.g. a new model rev).