Tolerance Stack-Up: Worst-Case and RSS

Worst-case tolerance = sum of the half-widths; statistical RSS = sqrt(sum of squares), always tighter. Three dims at +/-0.005 -> +/-0.015 worst-case, +/-0.00866 RSS; a 0.020 gap fits 0.005-0.035 (WC) or 0.0113-0.0287 (RSS). The RSS benefit widens as the chain grows. A design aid; the drawing tolerances govern.

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Formula and source

tol_wc = sum(|tol_i|); tol_rss = sqrt(sum(tol_i^2)); gap = nominal +/- tol.

Worst-case and RSS (root-sum-square) tolerance stack-up, standard mechanical-design / GD&T practice, by name.

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