Coffee Grinder Burr Alignment: How and Why It Matters

Volume I  ·  May 2026  ·  467 words

Burr alignment — the degree to which the two grinding burrs are parallel to each other — determines the uniformity of the grind particle size distribution. When burrs are misaligned, one side of the burr gap is narrower than the other, producing a mixture of fine particles from the narrow side and coarse particles from the wide side. The resulting distribution is wider than the grinder's design specification, producing simultaneous over-extraction (from fines) and under-extraction (from boulders) in the same shot. Misalignment of 0.05 mm — the thickness of a human hair — can measurably degrade espresso extraction uniformity.

The standard diagnostic is the dry-erase marker test. The outer edge of one burr is coated with a non-permanent marker, the grinder is reassembled and run briefly at the touch-point (the finest setting where burrs just contact), and the pattern of marker removal is inspected. Even marker removal around the full circumference indicates good alignment. Marker remaining on one side indicates a tilt in the burr carrier — the burr is closer to the opposing burr on the unmarked side, preventing contact where the marker remains. The fix is shimming: placing thin metal foil (aluminum foil, typically 0.01–0.02 mm thick) under the burr mounting screws on the side that contacts early, tilting the burr into parallelism.

Factory alignment varies considerably between grinders and between individual units of the same model. The Baratza Encore ESP and similar entry-level grinders typically arrive with acceptable but not perfect alignment — good enough for espresso but improvable. Premium hand grinders like the 1Zpresso JX-Pro generally have tighter factory alignment due to the simpler mechanical path between the burr axle and the adjustment mechanism. For users who have dialed in their grind, dose, and tamp and still experience inconsistent shots, burr alignment is the most likely remaining variable — and the least frequently checked.