| 1 | Manufacturing Process | Confirm that the supplier controls raw-material preparation, cold forming or machining, thread production, heat treatment, surface finishing, and final inspection. | Review a process-flow chart, production records, machine list, operator instructions, and an on-site or live video audit. | Documented process flow with traceable inspection points | 18% | To Be Verified |
| 2 | Material Traceability | Verify the grade, heat number, chemical composition, and incoming inspection records for steel or stainless-steel wire and bar stock. | Request material mill certificates and compare heat numbers with production and packing records. Use a third-party PMI test when necessary. | 100% batch-level traceability for production lots | 15% | To Be Verified |
| 3 | Dimensional Accuracy | Check thread diameter, pitch, flange diameter, nut height, across-flats dimension, bearing surface, and concentricity against the approved drawing or applicable standard. | Use calibrated thread gauges, micrometers, vernier calipers, height gauges, and optical or coordinate measuring equipment. | All critical dimensions within drawing tolerances | 17% | To Be Verified |
| 4 | Mechanical Performance | Verify proof load, hardness, tensile performance where applicable, and resistance to thread stripping according to the specified nut property class. | Review laboratory reports and perform testing through an accredited independent laboratory. Select the test standard according to the required property class. | Results meet the approved specification and applicable ISO or ASTM requirements | 18% | To Be Verified |
| 5 | Thread and Torque Control | Confirm smooth assembly, thread fit, prevailing torque where specified, and the absence of cross-threading, burrs, or damaged threads. | Perform go/no-go gauge inspection, assembly trials with mating bolts, and torque testing based on the purchase specification. | No rejected thread gauges; torque values remain within the agreed range | 12% | To Be Verified |
| 6 | Surface Treatment and Corrosion Protection | Check coating type, coating thickness, appearance, adhesion, hydrogen-embrittlement controls where relevant, and corrosion resistance requirements. | Review coating-process records and test reports. Use coating-thickness measurement, adhesion testing, and salt-spray testing only when required by the specification. | Coating meets the agreed thickness, appearance, and corrosion requirement | 10% | To Be Verified |
| 7 | Quality Management System | Determine whether the supplier operates controlled procedures for document management, nonconforming products, corrective actions, calibration, and customer complaints. | Request a current quality-management certificate, audit summary, calibration records, and anonymized corrective-action reports. | Current ISO 9001 certification or equivalent documented controls | 5% | To Be Verified |
| 8 | Capacity and Production Stability | Verify whether the supplier can maintain the required monthly volume, tooling availability, lead time, and continuity of production. | Review capacity records, equipment utilization, tooling plans, production schedules, and sample delivery performance. | Capacity exceeds forecast demand with documented contingency planning | 5% | To Be Verified |