Build a 1-D chain of dimensions, mark each one as adding to or subtracting from the gap, and get the nominal result plus both worst-case and statistical (RSS) limits. Tolerances entered as equal ± (symmetric).
| Feature | Nominal | + tol | − tol | Direction |
|---|
Worst case sums every tolerance — guaranteed but conservative; if it fits worst-case, it always fits. RSS = √(Σ tol²) assumes independent, centred, normally-distributed parts — tighter and realistic for volume production, but a small fraction can fall outside it. Use worst-case for safety-critical or low-volume; RSS for high-volume where you control the process. This is a 1-D tool: all dimensions must lie along one axis.