Tolerance Stack-Up
Calculate the final assembly gap or interference by stacking component dimensions. Use positive (+) for gaps/housings and negative (-) for shafts/inserts.
| Dir | Description | Nominal (in) | + Tol (in) | - Tol (in) |
|---|
Assembly Gap Analysis
Worst-Case (Absolute)
Maximum Gap:
0.0000
Minimum Gap:
0.0000
Total Spread:
0.0000
Statistical (RSS)
Probable Max:
0.0000
Probable Min:
0.0000
Total Spread:
0.0000
0
Gap Visualization
+
Worst Case
RSS
Mean
Stack-Up Methodology
Worst-Case Analysis
Assumes that every single part in the assembly is machined to its absolute worst permissible limit simultaneously. This guarantees 100% part interchangeability, but often forces extremely tight, expensive tolerances on the drawing.
Root Sum Square (RSS)
Statistically, it is highly improbable that every part in an assembly will be at its worst-case limit at the same time. The RSS method assumes a normal (Gaussian) distribution of parts.
$Tol_{RSS} = \sqrt{T_1^2 + T_2^2 + T_3^2 + ...}$
By using RSS, engineers can safely open up tolerances on individual parts, significantly reducing manufacturing costs, while maintaining a 99.7% (3-sigma) assembly success rate.
Direction (+ / -)
- Positive (+): Dimensions that increase the final gap (e.g., the inner width of a housing).
- Negative (-): Dimensions that decrease the final gap (e.g., shafts, washers, bearings inside the housing).