ISO 6149-3:2006

Overview - ISO 6149-3:2006 (stud ends, L series)

ISO 6149-3:2006 specifies the dimensions, design, test methods and requirements for light‑duty (L series) stud ends and matching O‑rings used in hydraulic fluid power and general‑use applications. It covers metric stud ends with ISO 261 metric threads and O‑ring sealing, for thread sizes from M8 up to M60, and defines performance limits, identification, and designation rules for adjustable and non‑adjustable stud ends.

Key topics and technical requirements

• Threading and dimensions: Stud ends conform to ISO 261 metric threads with specified dimensions and hex tolerances (product grade C) referenced to ISO 965‑1 and detailed in the standard’s figures and tables.
• Stud end types: Distinguishes adjustable (orientation via locknut) and non‑adjustable (straight) stud ends with identification machined features.
• Working pressures and test pressures:
  • Non‑adjustable stud ends: up to 40 MPa (400 bar) (size dependent).
  • Adjustable stud ends: up to 31.5 MPa (315 bar) (size dependent).
  • Burst and impulse (cyclic endurance) pressures are specified per thread size (see Table 2).
  • Pressure ratings were established using connectors of low carbon steel; actual permissible pressure depends on size, material and application.
• O‑rings: Dimensions and material guidance: default O‑ring material for petroleum‑based hydraulic fluids is NBR (nitrile), hardness 90 ± 5 IRHD, meeting ISO 3601‑3 quality criteria.
• Performance testing: Burst and cyclic endurance (impulse) tests performed in accordance with ISO 19879. Manufacturers are required to verify rated performance by testing; conformance to dimensional data alone does not guarantee performance.
• Washer and locknut requirements: Flatness, fit, and maximum nut torque to move adjustable washers are specified (Table 3).
• Marking and designation: Clear designation format (e.g., “Stud end ISO 6149‑3 - M18 × 1,5”) and identification features for metric stud ends are defined.

Practical applications

• Hydraulic system connectors on tubes, pipes, hoses and hose fittings where metric threads with O‑ring sealing are needed.
• Typical use in mobile and industrial hydraulics, fluid power equipment, valves, manifolds and diagnostic ports.
• Useful where compact, light‑duty connections are required and pressure/size limits match the application.

Who should use this standard

• Hydraulic system designers and engineers specifying connectors and ports.
• Manufacturers of connectors, fittings and O‑rings for hydraulic equipment.
• Quality assurance and test laboratories performing burst and impulse tests.
• Procurement and compliance teams ensuring components meet international requirements.

Related standards

• ISO 6149 (Parts 1, 2, 4) - series for ports and stud ends (heavy‑duty S series is Part 2).
• ISO 19879 - test methods for hydraulic fluid power connections.
• ISO 3601‑3 - O‑ring quality acceptance criteria.
• ISO 261 / ISO 965‑1 - metric thread definitions and tolerances.

Using ISO 6149‑3:2006 helps ensure consistent dimensions, reliable O‑ring sealing and validated pressure performance for light‑duty hydraulic stud ends.