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We assemble four spacers end to end inside a machined pocket. Quality inspection has accepted the individual parts, but some combinations fit freely while others need force.
The dimensions we are working with
- Each spacer: 10.00 mm ± 0.10 mm along the stacking direction.
- Pocket length: 40.20 mm ± 0.10 mm.
- Assembly requirement: at least 0.05 mm total end clearance, with no press fit intended.
The nominal dimensions leave clearance, so I suspect our drawing review missed the tolerance stack-up. We need interchangeable parts rather than an operator selecting spacers until a set fits.
Should this be assessed using worst-case tolerance analysis, or could a statistical tolerance stack-up be justified for production? What measurement data and assumptions would be needed before trusting the statistical approach?
I would like to understand how to set tolerances around the assembly requirement without unnecessarily tightening every component dimension.
