Overview
ISO 2702:2022 - "Fasteners - Heat treated tapping screws - Mechanical and physical properties" defines the mechanical and physical requirements and test methods for steel, heat‑treated tapping screws with thread sizes ST2,2 to ST9,5 (ISO 1478), tested at ambient temperatures 10 °C to 35 °C. The standard covers properties after heat treatment (surface/core hardness, case‑hardened depth, microstructure), functional tests (thread‑forming ability, torsional strength, ductility/drive tests), inspection, and marking/packaging requirements.
Key topics and requirements
- Scope and materials
- Applies to tapping screws made of cold‑heading steel suitable for case‑hardening.
- Hardness
- Minimum surface hardness: 450 HV 0,3 (Vickers HV 0.3).
- Core hardness: 270 HV to 390 HV (HV5 for threads ≤ ST3,9; HV10 for threads > ST3,9).
- Purchaser may specify lower maximum hardness to mitigate environmental hydrogen embrittlement (EHE).
- Case‑hardened depth (CHD)
- CHD specified by thread size groups (examples):
- ST2,2–ST2,6: 0.04–0.12 mm
- ST3,9–ST5,5: 0.10–0.23 mm
- ST6,3–ST9,5: 0.15–0.28 mm
- CHD determined by Vickers hardness profile to the 420 HV 0,3 threshold.
- Mechanical performance
- Torsional (breaking) torque specified per thread (examples: ST2,2 = 0.45 Nm; ST9,5 = 68.0 Nm).
- Thread‑forming ability: screws must form mating threads in sheet metal without deforming their own thread.
- Ductility: head must remain attached to shank under prescribed test conditions.
- Test methods and inspection
- Test methods are in Clause 6 (surface/core hardness per ISO 6507‑1, CHD, microstructure, drive test, torsional and ductility tests).
- Clauses on manufacturer, supplier and purchaser inspection and delivery of test results.
- Marking and labelling
- Requirements for marking on screws and packaging are specified to support traceability.
Applications
ISO 2702:2022 is used to ensure reliable performance of heat‑treated tapping screws in sheet‑metal assemblies where thread‑forming behaviour and controlled hardness/case depth are critical. Typical applications include:
- Sheet metal fabrication and enclosure assembly
- Electronics and appliance manufacturing
- HVAC, automotive trim and interior components
- Building contractors and fastening system suppliers
Who uses this standard
- Fastener manufacturers and heat‑treatment shops (quality control and product specification)
- OEM engineers and design teams specifying fasteners
- Procurement and quality inspectors (acceptance testing and supplier verification)
- Test laboratories performing hardness, metallography and torsion testing
Related standards
ISO 2702:2022 helps ensure consistent, testable mechanical properties and reproducible performance for heat‑treated tapping screws across industries.
