Tolerance Stack-Up Assistant
Calculate worst-case and RSS (root-sum-square) tolerance accumulation across a chain of dimensions. Critical for checking if assembled parts will fit and function.
Stack-up methods
Worst-case: total tolerance = sum of all individual tolerances. Assumes every dimension is at its extreme simultaneously. Safe but conservative — can require very tight individual tolerances.
RSS (Root Sum Square): total tolerance = √(Σ tol²). Statistically realistic assuming normal distributions and ~Cpk 1.33. Allows looser individual tolerances, lower cost.
Rule of thumb: if the assembled gap is critical (seal, bearing fit), use worst-case. If it's a cosmetic or non-critical gap, RSS is fine. Always draw the dimension chain and identify which dimensions stack up in the same direction.