ISO 11926-3:1995

Overview

ISO 11926-3:1995 specifies dimensions, performance requirements and test procedures for adjustable and non‑adjustable light‑duty (L series) stud ends with ISO 725 threads and O‑ring sealing, intended for general use and fluid‑power applications. The part covers physical dimensions, material guidance, O‑ring geometry and hardness, burst and cyclic endurance tests, washer flatness and torque limits, and the designation format for stud ends.

Key topics and technical requirements

• Scope: Applies to L‑series stud ends and their related O‑rings for connections to ports complying with ISO 11926 family. Stud ends may be used at working pressures up to 31.5 MPa (315 bar) depending on size, material and application.
• Dimensions & tolerances: Stud end geometry and hex tolerances follow ISO 725 and ISO 5864 (tolerance class ZA). Detailed sizes, flats and clinch washer design are specified in figures and tables.
• Materials: Stud ends are made from low‑carbon steel and are plated. Test blocks for burst testing are hardened to 50–55 HRC.
• O‑rings: Recommended material is nitrile (NBR) with hardness (90 ± 0.5) IRHD, conforming to ISO 3601‑3 quality grade N; inside and cross‑section diameters are specified per thread size.
• Performance tests:
  • Burst test: At least three samples; confirm a minimum 4:1 burst-to-working pressure ratio. Pressure rise rate and lubrication procedures are defined.
  • Cyclic endurance (impulse) test: Six samples tested at specified impulse pressures and a cycle rate of 0.5–1.3 Hz following ISO 6803 waveform; requirement is 1,000,000 cycles.
  • Test procedures include specified test torques (see test table), lubrication with hydraulic oil VG32, and reporting on the normative test data form (Annex A).
• Washer and locknut: Adjustable stud end washer clinch, flatness allowances and maximum nut torques are specified to ensure proper sealing and orientation.
• Designation: Stud ends are designated in the form “Stud end ISO 11926‑3 – – ” (example: Stud end ISO 11926‑3 – 1/2 – 20).

Applications and who uses this standard

ISO 11926‑3 is intended for:

• Hydraulic and pneumatic component manufacturers (fittings, shaped fittings, hose fittings)
• Fluid‑power system designers and OEMs specifying stud‑end connections
• Quality and testing laboratories performing burst and impulse qualification
• Procurement and standards teams specifying compliant connection hardware

Typical applications include low‑ to moderate‑pressure fluid conveyance and fittings where ISO 725 threaded stud ends with O‑ring sealing are required and where light‑duty mechanical strength and cyclic endurance are acceptable.

Related standards

• ISO 11926‑1 (Ports with O‑ring seal in truncated housing)
• ISO 725 (inch screw thread basic dimensions)
• ISO 3601‑3 (O‑ring acceptance criteria)
• ISO 5864, ISO 4759‑1, ISO 3448, ISO 6803, ISO 5598 (related tolerances, terminology, test methods)

Note: ISO 11926‑3 provides dimensional and test guidance but manufacturers should perform full qualification testing per the standard. For new hydraulic designs, ISO 6149 is the recommended thread/port standard.