ISO 6788:1997 PDF

Overview

ISO 6788:1997 specifies dimensional and test requirements for four-way socket wrenches used for assembling screws and nuts on trucks and cars. The second edition (1997) defines socket head dimensions (in millimetres) for four designated wrench types and prescribes a torque test procedure to verify tool performance. The standard targets manufacturers, designers, quality engineers and procurement professionals involved with hand assembly tools.

Key topics and requirements

• Dimensions and tolerances
  • Socket head dimensions are given in millimetres for four wrench types (illustrated in the standard).
  • Tolerances on wrench openings follow ISO 691 ("unmachined closed" series).
  • Driving squares must conform to ISO 1174-1.
  • Maximum outside head dimensions are specified as 10% greater than values given in ISO 2236.
  • Half-arm lengths must be equal within a tolerance of –3% of the nominal length, and the arm angle is 90° – 2°.
• Material hardness
  • Minimum hardness requirements for sockets and male driving squares reference ISO 1711‑1 and ISO 3316, respectively.
• Torque testing
  • Torque tests are performed by placing the socket or square drive over the appropriate test mandrel and applying the corresponding torque values referenced in ISO 1711‑1 (for hexagonal sockets) and ISO 3316 (for square drives).
  • A support must be used to avoid bending moments caused by the arm length (distance l/2) during the test.
  • After testing, the wrench must show no permanent deformation or defects that could affect use.
• Designation and marking
  • Example designation formats are provided (e.g., Wrench ISO 6788 – 18 × 21 × 22 × 24, or Wrench ISO 6788 – 18 × 21 × 22 × A 12,5).
  • Tools must be permanently and legibly marked with at least the width across flats and the manufacturer’s name or trademark.

Applications and users

• Practical for tool manufacturers, quality-control labs, and tool designers specifying dimensional and mechanical requirements for four-way socket wrenches.
• Used by automotive and truck assembly operations, maintenance workshops, and procurement teams to ensure interchangeability, safety and durability of hand tools.
• Useful for standards committees and test houses establishing compliance and product certification.

Related standards

• ISO 691:1997 (wrench and socket opening tolerances)
• ISO 1174-1:1996 (driving squares for hand socket tools)
• ISO 1711-1:1996 (technical specs for hand wrenches and sockets)
• ISO 2236:1991 (maximum outside head dimensions)
• ISO 3316:1996 (attachments and tests)
• ISO 1703 (nomenclature for assembly tools)