How to inspect machined parts

01Prepare from the drawing

Confirm the drawing revision, dimensioning standard (ISO or ASME), general tolerances, surface texture requirements, material and heat treatment, coatings and notes. Identify critical characteristics and datums before touching a part.

02Inspection checklist

• Identification, marking and traceability
• Material certificate and heat treatment record
• Critical diameters and lengths with suitable instruments
• Geometrical tolerances relative to datums
• Threads with go and no-go gauges
• Surface roughness where specified
• Edges, burrs and sharp corners
• Visual damage, chatter marks, tool marks
• Cleanliness and residues
• Corrosion protection and packing

03Measurement method matters

A two point diameter measurement and a least squares cylinder are different results. Position tolerances depend on datum alignment. When results disagree with the supplier, the method is usually the cause. See dimensional measurement and CMM measurement.

04Report actual values

Report measured values, the instrument used and the result. 'OK' alone hides trends and makes concessions harder to evaluate.