Overview
ISO 4757:1983 - Cross recesses for screws specifies the geometry and gauging methods for cruciform (cross) recesses used in screw heads. First published in 1983 by ISO/TC 2 (Fasteners), the standard defines two recess forms - recess type H and recess type Z - provides illustrative figures, tabulates gauge dimensions for No. 0 up to No. 4, and describes a method for penetration gauging to assess recess usability.
Key topics and technical requirements
- Recess types: Clear definitions and drawings for type H and type Z cross recesses, with theoretical dimensions shown in millimetres.
- Gauge dimensions: Tabulated gauge requirements for gauges No. 0–4. Dimensions are given as theoretical values and include minimum/maximum limits where applicable.
- Penetration gauging method:
- The gauge point corresponds to the screwdriver point; a sleeve guides the gauge and establishes a reference plane.
- For type H, the standard specifies a minimum penetration depth (test dimension) indicated in product standards.
- For type Z, both minimum and maximum penetration depths are referenced in product standards.
- The penetration depth is measured from the reference plane using a dial gauge; zero and control positions are established on a flat surface.
- Reference plane definition: The plane passes through the intersection point of recess wings and the top surface of a flat-head screw. For crowned heads, the reference plane is fixed using the gauge sleeve’s bearing surfaces.
- Inspection tolerance note: The standard notes possible measurement inaccuracy due to permissible errors in core thickness of the gauge point (document cites possible inaccuracy up to ~0.13 mm).
Practical applications
- Ensures consistent manufacture of cruciform recessed screws and matching screwdrivers.
- Provides requirements for quality control and acceptance testing in fastener production and assembly lines.
- Guides tooling designers and gauge makers on dimensional and functional criteria.
- Useful for procurement and compliance verification in industries using fasteners (automotive, electronics, machinery, construction).
Who should use this standard
- Fastener manufacturers and suppliers
- Quality and inspection labs
- Tooling and gauge designers
- Mechanical engineers specifying screw fasteners
- Purchasing and compliance teams ensuring interchangeability
Related standards
- ISO 4757 complements other ISO fastener and screw head standards (product-specific standards reference penetration depths and other acceptance criteria). For complete compliance, consult applicable product standards and ISO fastener series.
