ISO 6264:1998

Overview

ISO 6264:1998 - "Hydraulic fluid power - Pressure‑relief valves - Mounting surfaces" specifies the mounting surface dimensions, tolerances and marking needed to ensure interchangeability of hydraulic pressure‑relief valves. Applicable to industrial hydraulic equipment, the standard defines the area, hole locations and surface characteristics for a range of valve sizes and both directly‑operated and pilot‑operated designs.

Key topics and technical requirements

• Mounting surface dimensions for pressure‑relief valves with main port diameters of 4.5 mm, 7.5 mm, 14.7 mm, 23.4 mm and 32 mm (several coded figures provide the exact layouts).
• Surface quality: recommended surface roughness Ra ≤ 0.8 μm and surface texture indication per ISO 468 / ISO 1302.
• Flatness: 0.01 mm over 100 mm (reference ISO 1101 geometric tolerancing).
• Hole tolerances: locating pin holes tolerance H12; positional tolerances along X/Y axes - pin and screw holes ±0.1 mm, port holes ±0.2 mm.
• Fixing screw guidance: minimum and recommended thread engagement depths and suggested thread lengths to improve interchangeability.
• Port marking and symbols: standardized graphic symbols for ports (direct and pilot‑operated valves) following ISO 1219‑1, with options for internal/external drains and pilot ports.
• Modular stacks: for modular stack valves the standard defers to ISO 4401 mounting surfaces and port marking.
• Obsolescence notes: some older mounting surface variants are marked obsolete and are not recommended for new designs.
• Identification statement: manufacturers are encouraged to declare conformity with ISO 6264 in catalogues and reports.

Practical applications and who uses it

ISO 6264 is used by:

• Hydraulic valve manufacturers - to design mounting flanges/carburets that are physically interchangeable with other suppliers’ valves.
• Manifold and subplate designers - to machine correct mounting pockets, locating pins and threaded holes for reliable installation.
• System integrators and OEMs - to select valves, ensure compatibility and simplify maintenance and spare‑parts stocking.
• Quality and inspection teams - to verify surface finish, flatness and hole tolerances during production and assembly.
• Maintenance and procurement - to confirm replacement valves will fit existing manifolds or subplates without rework.

Related standards

• ISO 4401 - hydraulic directional valve mounting (modular stack compatibility)
• ISO 468, ISO 1302 - surface roughness and texture specification
• ISO 1101 - geometric tolerancing (flatness, form)
• ISO 1219‑1 - fluid power graphic symbols
• ISO 5598 and ISO 5783 - vocabulary and valve mounting identification codes

Using ISO 6264 helps ensure interchangeability, reduces rework and eases supply-chain management for hydraulic pressure‑relief valves across industrial applications.