ISO 4395:2009

Overview

ISO 4395:2009 - "Fluid power systems and components - Cylinder piston rod end types and dimensions" defines a standard series of piston rod end types and associated dimensions for cylinders used in hydraulic and pneumatic fluid power systems. The standard specifies accepted thread types and lengths for male and female piston-rod threads, and the dimensions and styles of wrench flats and hook wrench holes used during assembly. ISO 4395:2009 updates the earlier 1978 edition and is intended to promote interchangeability and safe assembly of cylinder rod ends across manufacturers.

Key topics and requirements

• Piston rod thread types: Standardized male and female thread configurations are defined for hydraulic and pneumatic cylinders, with recommended minimum and maximum thread lengths (short, middle, long types) to suit different mounting and adjustment needs.
• Thread dimensions and selection: Thread sizes and lengths are presented in tabular form for common metric threads used in fluid power cylinders; hydraulic and pneumatic applications have separate tables and figures.
• Wrench flats and hook-wrench holes: Where assembly requires holding or rotating the rod end, ISO 4395 specifies minimum dimensions and styles (wrench flats or hook-wrench holes) and requires at least two flats/holes when needed.
• Identification guidance: The standard recommends a formal identification statement for catalogs and test reports to indicate conformance: selection of piston rod end dimensions in accordance with ISO 4395.
• Normative coordination: Uses term definitions and dimension-letter symbols per ISO 5598 and ISO 6099 for consistency.

Applications and practical value

• Ensures interchangeability of piston rod ends and accessories (clevises, rod eyes, nuts) across manufacturers.
• Guides designers and engineers when specifying cylinder rod-thread geometry for hydraulic actuators and pneumatic cylinders.
• Helps manufacturers determine appropriate thread lengths (short/middle/long) when locknuts or adjustments are required and when to include wrench flats or hook-wrench holes for safe assembly.
• Useful for procurement, quality, and maintenance teams to verify compatibility and document conformance in technical literature.

Who uses ISO 4395:2009

• Hydraulic and pneumatic cylinder manufacturers
• Mechanical design and systems engineers specifying actuators
• Maintenance and reliability engineers replacing cylinder components
• Purchasing and standards compliance personnel

Related standards

• ISO 5598 - Fluid power systems and components: Vocabulary
• ISO 6099 - Cylinders: Identification code for mounting dimensions and types
• ISO 3320 - Cylinder bores and piston rod diameters (metric series)

Keywords: ISO 4395:2009, piston rod end, cylinder piston rod, thread dimensions, wrench flats, hook wrench holes, hydraulic cylinder, pneumatic cylinder, fluid power systems.