SIST EN 3325:2008

Overview

SIST EN 3325:2008 is a European standard developed by the Slovenian Institute for Standardization (SIST) for bolts used in aerospace applications. Officially titled Aerospace series - Bolts, T-head, relieved shank, long thread, in heat resisting steel, FE-PM1708 (FV535) - Classification: 1 000 MPa/550 °C - Unplated, this standard specifies the characteristics and technical requirements for T-head bolts made from FE-PM1708 (FV535), a high-performance heat resisting steel. These bolts are designed to function reliably under high mechanical loads and elevated temperatures up to 550°C.

Key Topics

• T-head Bolt Design: Specifies T-head bolts with a relieved shank and extended thread, engineered for optimal performance and installation versatility in aerospace assemblies.
• Material Requirements: Covers the use of FE-PM1708 (FV535), a heat-resistant steel known for its high tensile strength (classified at 1 000 MPa) and consistent mechanical properties at elevated temperatures.
• Dimensional Consistency: Outlines dimensions, tolerances, and mass for different bolt variants, supporting uniformity and compatibility across aerospace applications.
• Technical Markings: Mandates product marking according to EN 2424 to ensure traceability and compliance within aerospace supply chains.
• Classification: Stipulates bolt performance at up to 1 000 MPa tensile strength and up to 550°C, making them suitable for high-stress, high-temperature environments.

Applications

Bolts compliant with SIST EN 3325:2008 are specifically designed for use in aerospace structures and components, where reliability, strength, and resistance to extreme conditions are critical. Typical applications include:

• Aircraft Structures: Used in primary and secondary airframe assemblies; the T-head design allows for efficient anti-rotation locking within slotted holes or under thin flanges.
• Engine Mountings: The heat resisting steel construction makes these bolts ideal for mounting components exposed to high thermal and vibrational loads near engines or exhaust systems.
• Mission-Critical Assemblies: Whether for satellites, spacecraft, or military aerospace platforms, the specification guarantees performance where failure is not an option.
• Maintenance and Retrofit: Standardized dimensions and designations ensure interchangeable replacements across a range of aerospace platforms.

The unplated finish of these bolts is often preferred in environments where secondary coatings could degrade or where weight savings and direct material contact are prioritized.

Related Standards

Bolts manufactured in accordance with SIST EN 3325:2008 complement other aerospace fastener and material standards, ensuring system compatibility and safety:

• ISO 3353-1: Aerospace - Lead and Runout Threads, relevant for rolled external threads in bolt manufacturing.
• ISO 5855-2: Aerospace - MJ Threads - Dimensional requirements for bolts and nuts, ensuring thread compatibility.
• EN 2424: Aerospace series - Marking of aerospace products, necessary for identification and traceability.
• EN 3302: Aerospace series - Bolts in heat resisting steel FE-PM1708 (FV535), specifying technical requirements for similar bolt types.
• EN 2493, EN 4244, EN 4245: Standards addressing material characteristics, production processes (such as vacuum arc remelting), and bar/forging stock requirements for FE-PM1708 steel.

Aligning with SIST EN 3325:2008 ensures that manufacturers and suppliers meet strict aerospace industry requirements for safety, quality, and reliability of T-head bolts under demanding operational conditions.

Keywords: SIST EN 3325:2008, aerospace bolts, T-head bolts, relieved shank, long thread, heat resisting steel, FE-PM1708, FV535, high tensile strength bolts, aerospace fastener standards, unplated bolts, EN 3302, aircraft assembly fasteners, high temperature bolts.