A tolerance is useful only when it protects a functional requirement and can be measured consistently. Good inspection planning therefore starts before production: the buyer and supplier should agree which features are critical, how the part is referenced, what condition it is measured in and what evidence must accompany the shipment.
Link each critical tolerance to function
Identify whether the feature controls fit, motion, sealing, alignment, load, appearance or another requirement. Apply tight limits selectively to the characteristics that influence that function. Over-tolerancing non-critical surfaces can add machining and inspection cost while obscuring the features that deserve the most control.
Build a clear datum strategy
The drawing datums should reflect how the part is assembled and inspected. A feature measured from different references can produce different results even when the physical part has not changed. Review datum accessibility, fixturing, part flexibility and whether the part is measured before or after heat treatment, coating or assembly.
Agree the measurement method
The instrument, contact strategy, environment, resolution and measurement uncertainty must be suitable for the requirement. CMM, height gauge, micrometer, bore gauge, surface instrument, optical system and functional gauge answer different questions. A nominally precise instrument does not automatically make every result comparable; the method and setup should be documented for critical characteristics.
Define sampling and records
State whether the order requires first-piece approval, first-article results, in-process checks, final dimensional reports, material records, surface data or process certificates. Sampling should reflect feature risk, process stability, batch size and customer requirements. If every unit must be checked for a particular characteristic, say so explicitly and define the acceptance record.
The quality documents guide lists the information needed to scope dimensional, material and first-article evidence. Management-system certificates have a different purpose; review their named entity and scope on the certifications page rather than treating a certificate as a substitute for part results.
Keep revision control visible
The quotation, process plan, inspection program and report should reference the same drawing revision. Engineering changes require a documented review of affected features, tooling, price, schedule and validation. Do not rely on an email description when a revised drawing or approved deviation is required.
Include the drawing revision, critical-characteristic list, measurement expectations, sampling and document format in the RFQ. Jinxi can review these inputs with the proposed machining route before confirming scope.