ISO 9974-3:1996

Overview

ISO 9974-3:1996 defines stud ends with metal-to-metal sealing (type B) for ports and stud ends using ISO 261 threads intended for general use and fluid power. The standard specifies dimensions, designation, performance requirements and test procedures for three duty series: extra-light (LL), light (L) and heavy (S). It also includes a normative test data form (Annex A) and an informative bibliography (Annex B).

Key topics and technical requirements

• Threading and dimensions: Stud ends follow ISO 261 general-purpose metric screw thread sizes and the dimensional tables provided in the standard.
• Duty series and working pressures: Design guidance and permissible working pressures depend on series and size (example ranges given in the standard: LL, L and S series ratings).
• Metal-to-metal sealing: Sealing is achieved by a machined metal sealing face; this causes sealing-face damage on assembly so re-use is not recommended - they may leak if re-used and are not suitable for leak-free hydraulic designs when re-used.
• Materials and hardness: Typical materials specified include low-carbon steel (plated) for stud ends and hardened, unplated test blocks (around 45–50 HRC) for qualification testing.
• Performance tests:
  • Burst pressure test - verifies burst-to-working pressure ratio (test samples and pressure rise rate defined).
  • Cyclic endurance (impulse) test - verifies resistance to pressure cycling (1,000,000 cycle requirement for qualifying samples).
  • Qualification torques and thread lubrication - test assembly torques and lubrication media (hydraulic oil VG32) are specified.
• Designation & identification: Standard prescribes a naming convention (e.g., “Stud end IS0 9974-3 - M10 x 1.5 S”) and an identification statement for literature and test reports.

Applications

• Used in fluid power systems (hydraulic and pneumatic) and general pressurized piping where metal-to-metal face sealing is acceptable.
• Typical applications: tube fittings, hose fittings, valves and other connectors where threaded stud ends connect to ports with ISO 261 threads.
• Not recommended for new hydraulic designs that require guaranteed leak-free re-assembly; other ISO parts (e.g., ISO 6149) are preferred for new hydraulic designs.

Who should use this standard

• Mechanical and hydraulic designers, fittings manufacturers, quality engineers and test laboratories specifying or qualifying stud ends with metal-to-metal sealing.
• Procurement and certification teams needing consistent design, test and designation rules for ISO 261-threaded stud ends.

Related standards

• ISO 9974-1, ISO 9974-2 (other parts of the series)
• ISO 261 (metric screw threads)
• ISO 8434 series, DIN 3852-1 (equivalent stud ends), ISO 6803 (impulse testing) - see Annex B bibliography for full cross-references.

Keywords: ISO 9974-3, metal-to-metal sealing, ISO 261 threads, stud ends, fluid power, hydraulic fittings, burst pressure, impulse test, cyclic endurance.