SIST EN ISO 3506-3:2025 PDF

Overview

EN ISO 3506-3:2025 (ISO 3506-3:2025) specifies the mechanical and physical properties of corrosion resistant stainless steel set screws and similar fasteners that are not subject to tensile stress. It covers fasteners made from austenitic and duplex stainless steels with defined grades and hardness classes and aligns metric thread, diameter and tolerance requirements with applicable ISO thread standards.

Scope highlights

• Applies to ISO metric threaded set screws (ISO 68-1) with diameter/pitch per ISO 261/262
• Nominal thread diameters from 1.6 mm to 24 mm
• Thread tolerances per ISO 965-1/965-2
• Covers specified hardness classes and any screw shape
• Excludes screws under tensile stress (see ISO 3506-1) and does not set functional properties such as shear strength or weldability

Warning: tests are performed at ambient 10 °C to 35 °C; intended service use is –20 °C to +150 °C. Properties outside these ranges are not guaranteed and must be verified by the user.

Key Topics and Requirements

• Designation system for stainless steel grades and hardness classes
• Materials: chemical composition, surface condition (finish/coating), corrosion resistance and magnetic properties
• Mechanical/physical requirements: hardness limits, proof torque for socket set screws
• Inspection: manufacturer’s, supplier’s and purchaser’s inspection provisions and delivery of test results
• Test methods: improved procedures for hardness testing and proof torque testing
• Marking and labelling requirements for traceability

The 2025 edition integrates duplex grades and updates structure to align with other ISO 3506 parts; annexes common to multiple parts are moved to ISO 3506-6.

Applications

EN ISO 3506-3:2025 is used where corrosion-resistant, non-tensile fasteners are required, for example in assemblies that need set screws for positioning, clamping or locking without bearing primary tensile loads. Typical practical uses include:

• Machinery assemblies and mechanical components
• Instrumentation and equipment in corrosive environments
• Design and procurement where specified stainless-steel grades and hardness are required for corrosion performance and fit

Who uses this standard

• Fastener manufacturers and heat-treatment processors
• Design engineers and product specifiers selecting corrosion-resistant fasteners
• Quality and inspection personnel validating hardness and proof-torque
• Procurement and compliance teams ensuring conformity with metric thread/tolerance norms

Related standards

• ISO 3506-1 (fasteners under tensile stress)
• ISO 3506-6 (general rules and detailed stainless steel properties)
• ISO 68-1, ISO 261, ISO 262, ISO 965-1 / ISO 965-2 (thread forms, pitches and tolerances)

Keywords: EN ISO 3506-3:2025, ISO 3506-3:2025, stainless steel set screws, corrosion resistant fasteners, hardness classes, austenitic stainless steel, duplex stainless steel, proof torque, hardness test.