Outoftolerance

Out-of-tolerance is a term used in quality assurance, metrology, and engineering to describe a measurement or feature that falls outside the allowable range defined by a specification, drawing, or standard. It indicates that the item does not meet the required requirements for fit, form, or function.

Tolerance defines the permissible deviation around a nominal value and is usually stated as lower and upper specification limits. If a measurement is below the lower limit or above the upper limit, it is considered out of tolerance. Tolerance bounds may be expressed in absolute units, percentages, or other metrics depending on the context.

Inspection and disposition: When an item is out of tolerance, it is typically classified as nonconforming. Depending on policy and severity, it may be reworked, repaired, scrapped, or rejected and returned to supplier. Documentation supports traceability, and an out-of-tolerance result often triggers corrective actions or deviation approvals within a quality management system.

Causes and mitigation: Common causes include tool wear, process drift, calibration error, material variance, and measurement error. Mitigation strategies involve regular calibration and maintenance, tighter process control, statistical process control, proper gage R&R (repeatability and reproducibility) studies, and, when justified, adjusting tolerances or specifications.

Context and note: In laboratories and calibration settings, out-of-tolerance may refer to instrument readouts or verification checks that exceed allowable error limits. Understanding, detecting, and appropriately dispositioning out-of-tolerance conditions is essential for maintaining product quality and process reliability.

See also: tolerance, nonconformance, corrective action, CAPA, quality management.