LEGO maintains 0.01mm mold tolerances across billions of bricks annually using wire EDM steel molds, ABS plastic with predictable 0.3-0.5% shrinkage, and cavity-level traceability—ensuring 66-year-old bricks fit perfectly with new ones from five global factories.

LEGO's 0.002mm Specification and It's Implications for Manufacturing

A 2x4 LEGO brick manufactured in 1958 will snap perfectly onto a brick molded this morning in Denmark, China, Hungary, Mexico, or the Czech Republic. The 66-year-old brick will have the exact same interference fit, the same clutch power, the same 4.8mm stud diameter. This is the result of maintaining mold tolerances to 0.01mm (10 microns) across billions of parts annually. For hardware engineers developing products with tight-fit mechanical interfaces, LEGO represents an extreme case study in wh...