Tolerance stack-up is why assemblies sometimes don’t fit. A few basics keep your designs buildable.
Worst-case adds every tolerance — safe but expensive. Statistical (RSS) assumes not everything is at the limit at once — realistic for volume.
A clear 3-2-1 datum scheme lets every supplier and inspector interpret tolerances the same way, which is half the battle.
Apply tight tolerances to features that affect function or fit; loosen the rest to cut cost and lead time.
For safety-critical or low-volume parts where a single bad assembly is unacceptable.
Yes — it separates form, position and datum control so tolerances are unambiguous.