Why Parts That Pass Inspection Still Don't Fit (Tolerance Stack-Up)

Every part passed inspection, every dimension is within tolerance, and the lid still won't close. Nobody made a mistake. This is tolerance stack-up: small allowed errors adding up across an assembly.

The video shows worst-case stacking, the root-sum-square method real products are designed with, why datums matter, and the fixes engineers reach for when a stack doesn't close.

In this video

• What a tolerance really promises
• Worst case versus root-sum-square
• Chain dimensions versus a single datum
• Shims, sorting, floating parts, and the cost of a decimal place