Tolerance stack-up decides fit before the first tooled part.

Year

2026

Client

BrahmWorks Insights

Mechanical

Black electronic enclosures arranged as a product family.

The Challenge

A tolerance stack-up is the arithmetic of every dimension that sits between a datum and a functional gap, alignment or clearance. It tells you the range that gap can take when each part is somewhere inside its own drawing tolerance. It is not a decoration on a title block, and it is not proof that the parts will be centred on nominal.

Two methods are in ordinary use. Worst case adds the tolerances and asks whether the function survives even if every part is at its bad limit together.

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Tolerance Stack-Up

What we did

Mechanical

Industry

Mechanical

Description

This Insights guide explains Tolerance Stack-Up for founders and engineering teams building hardware that must be manufactured, tested, and handed off. Two methods are in ordinary use. Worst case adds the tolerances and asks whether the function survives even if every part is at its bad limit together. It also covers what goes into the chain; worst case; root-sum-square, and when it lies.

Round handheld device prototype packed in a moulded pulp tray

Concept product models and drawings on a workbench.

Hydroponic and BrahmEarth components on an assembly bench.

The Outcome

The function is one sentence, with a numeric window and a unit. Every contributor has a nominal, a tolerance and a sign. Both drawings share the datum in words, not two convenient edges.

“A tolerance stack-up is the arithmetic of every dimension that sits between a datum and a functional gap, alignment or clearance.”
BrahmWorksHardware practice note