When is a part considered a reject in machining?

A part is considered a reject in machining when its dimensions are out of tolerance. This means that the part does not meet the specified measurements required by the engineering drawing or blueprint. Adhering to precise dimensions is critical in machining because even small deviations can affect the functionality, assembly, and overall performance of the final product. Tolerances are established to ensure parts fit together correctly and operate as intended within a system.

While surface blemishes, missing components, and not being painted can be issues, they typically do not disqualify a part from being functional. Surface blemishes could potentially be polished out, missing components can be added later, and a lack of paint might affect aesthetics or corrosion resistance but does not directly impact the core function or fit of the part. In contrast, out-of-tolerance dimensions represent a fundamental issue that compromises the part’s usability and integrity, making it a clear reject in the machining process.