Tolerance Stack-Up, Start to Finish: Worst Case, RSS and Monte Carlo

The full method, start to finish, on one real gearbox assembly. We name the gap that matters, draw the loop with its signs, run worst case, root-sum-square and a Monte Carlo simulation, and watch the formula fail when a supplier runs off-centre.

Then the design side: datums and position tolerance, bonus tolerance, fixed and floating fasteners, the five fixes for a stack that doesn't close, thermal growth, and where tolerance money actually works.

In this video

• Tolerance, capability and the ±3σ convention
• The loop and its signs on a real assembly
• Worst case 0.15–0.69 versus RSS 0.28–0.56, and re-centring the nominal
• Monte Carlo and the 1.5× safety factor
• Datums, position tolerance, bonus tolerance, fastener fits
• Shorter chains, shims, selective assembly, floating parts, sensitivity
• The cost of a decimal place and thermal growth