Overview
EN ISO 10664:2014 - "Hexalobular internal driving feature for bolts and screws" (adopted by CEN) defines the shape, basic dimensions and gauging method of hexalobular internal driving features used in bolts and screws. The standard specifies the contour curvature (by GO and NO GO gauges), basic socket sizes and gauging rules needed for inspection. It is explicitly intended for inspection and designation, not as a manufacturing specification.
Key topics and requirements
- Basic dimensions: Nominal socket sizes and associated dimension data are listed (see Table 1). Key dimensions include A, B and related radii and depths.
- Gauging principle: Inspection uses a GO gauge that must fully enter the driving feature to the required penetration depth, and NO GO gauges that must not enter beyond the permitted fallaway allowance.
- GO and NO GO gauges: Detailed limiting dimensions for GO gauges (Tables 3) and NO GO gauges (Tables 4 and 5) define the contour curvature and limits for inspection of A, B and R dimensions.
- Fallaway allowance: Specific fallaway allowances per socket number are provided (Table 2). Gauging is referenced to the top surface of the head.
- Counterbore and penetration: Counterbore limits and reference to penetration depth (as specified in the relevant product standard) are given.
- Designation: How to designate a hexalobular feature (example: “Hexalobular internal driving feature ISO 10664 – 20”).
- Drawing guidance: Annex A gives illustrative correlations useful for CAD drawing of the hexalobular contour.
Applications and users
This standard is primarily used for quality inspection and acceptance of internal hexalobular sockets in bolts and screws. Typical users:
- Quality and inspection engineers in fastener production and assembly operations
- Test laboratories and conformity assessment bodies auditing fastener geometry
- Design and product engineers specifying inspection criteria for fastened assemblies
- Standardization bodies and purchasing/specification teams requiring unambiguous inspection rules
Practical uses include accepting incoming fasteners, validating assembly tooling fit, and defining inspection procedures for internal driving features.
Related standards and notes
- Prepared by ISO/TC 2 (Fasteners) and adopted by CEN as EN ISO 10664:2014. It supersedes EN ISO 10664:2005.
- EN ISO 10664:2014 is an inspection standard; manufacturing tolerances and production methods are governed by relevant fastener product standards and manufacturer specifications.
- See relevant product standards for required penetration depth and overall fastener dimensions.
Keywords: EN ISO 10664:2014, hexalobular internal driving feature, GO gauge, NO GO gauge, gauging, fasteners inspection, socket sizes, fallaway allowance.
