Overview
ISO 7379:1983 specifies the form and basic requirements for hexagon socket head shoulder screws (also called centring or shoulder screws) with metric dimensions. The standard covers nominal shoulder diameters from 6.5 mm up to and including 25 mm, gives the required geometrical tolerances, and provides an example for official designation and referencing.
This standard is intended to ensure interchangeability, consistent manufacturing, and correct use in assemblies where precise shoulder diameter and location are important.
Key Topics
- Scope: Metric shoulder screws with nominal shoulder diameters 6.5–25 mm. The document defines shape variants, head forms (smooth or knurled), and permissible edge chamfers or rounding.
- Geometrical tolerances: Concentricity, perpendicularity and straightness tolerances between head, shoulder and threaded portions are specified to control dimensional relationships and ensure fit and function.
- Materials and mechanical class: Material requirements are linked to international references (ISO 898/1). The standard notes that, due to their configuration, these screws cannot be subjected to a standard tensile test but must meet the other material and property requirements of class 12.9 per ISO 898/1.
- Surface finish and coatings: A surface roughness Rz/Ra and finish guidance is referenced (ISO 1302). Typical finishes include black oxide (chemical or thermal) and electrolytic coatings meeting ISO 4642.
- Designation and example: The standard gives an example designation format: Vis ... ISO 7379 - 10 x 40 for a shoulder screw with shoulder diameter 10 mm (M8 thread) and nominal length 40 mm.
Applications
ISO 7379 shoulder screws are used where a precise shoulder acts as a shaft, pivot, spacer or locating surface. Typical applications include:
- Precision assemblies and locating elements in jigs and fixtures
- Machine components requiring a controlled bearing surface or alignment feature
- Indexing pins and pivot points in mechanical linkages
- Fastening situations where a defined unthreaded section controls position or clearance
Benefits for design and procurement include improved interchangeability, reliable assembly tolerances, and clearer supplier requirements for material and finish.
Related Standards
ISO 7379 references and aligns with several international standards to cover threads, tolerances, finishes and inspection:
- ISO 261 - Metric threads: general overview, nominal lengths and thread lengths
- ISO 888 - Bolt, screw and stud lengths and related sizing
- ISO 898/1 - Mechanical properties for fasteners (material classes like 12.9)
- ISO 965 - Metric thread tolerances
- ISO 1302 - Indication of surface texture (roughness) on drawings
- ISO 3269 - Acceptance inspection for fasteners
- ISO 4642 - Electrolytic coating requirements for fasteners
- ISO 4759/1 - Tolerances for fasteners (part 1)
For designers, manufacturers and procurement teams, ISO 7379 is a practical reference for specifying shoulder screws correctly in metric designs where dimensional accuracy and assembly performance are critical.
