What is a key practice to manage tolerance stack-up during engine assembly?

• A. Rely solely on experience with no measurement plan.
• B. Implement a careful measurement plan and perform rework if necessary.
• C. Increase all tolerances to maximum values.
• D. Defer tolerancing until after engine run-in.

Answer: (B)

Managing tolerance stack-up comes down to planning how you measure and then correcting as needed. A careful measurement plan defines which critical dimensions must be checked, how they’re measured (tools and fixtures), what tolerances are acceptable, and what steps trigger rework. In engine assembly, many small tolerances line up across components—bores, journals, seals, and mating faces—so even if each part is within spec, the sequence can create interference or excessive looseness if not monitored. By measuring at key interfaces and applying rework when a dimension is out of tolerance, you keep all fits within designed limits and maintain proper clearances, loads, and sealing behavior. This approach provides verifiable control over stack-up and prevents later operational problems.

Relying only on experience without a plan isn’t reliable or auditable, because it can miss accumulative errors. Deferring tolerancing until after run-in can’t correct improper fits and may cause damage or wear. Increasing all tolerances to maximum just sacrifices performance and reliability.