This part of IS 1367 specifies the acceptance inspection procedures, sampling plans, and Acceptable Quality Levels (AQL) for threaded steel fasteners like bolts, screws, and nuts. It provides the statistical framework for buyers and QA/QC teams to accept or reject delivered lots based on dimensional tolerances and mechanical properties.
Specifies acceptance inspection procedures for fasteners according to ISO 3269.
Quick Reference Values
applicable thread diameterUp to M39
regular nut property classes4, 5, 6, 8, 9, 10, 12
thin nut property classes04, 05
temperature rangeTested at 10 to 35 °C
Key Formulas
F = As × Sp (Proof Load = Nominal stress area × Proof stress)
Practical Notes
Always match the nut property class to or higher than the bolt property class (e.g., use a Class 8 nut for a Class 8.8 bolt) to prevent thread stripping.
In case of a dispute, the proof load test is the decisive acceptance criterion over hardness testing.
This standard applies to standard nuts but excludes those requiring special properties like weldability, extreme temperature resistance, or corrosion resistance.