Introduction
The IMK is a Notified Body (NB 1647) within the EU and performs certification procedures for manufacturers’ production control systems (Factory production control – FPC) according to harmonized standards for bolting assemblies to be installed in building structures:
- Non-preloaded structural bolting assemblies – Part 1: General requirements,
- EN 14399-1: High strength structural bolting assemblies for preloading – Part 1: General requirements
Head of OE TSN
robert.cvelbar@imk.si
+386 1 280 21 14
+386 31 382 698
Testing of the screw material
An integral part of the manufacturer’s production control system is the implementation of initial type tests and tests for the monitoring of production. Bolting material tests can be performed at IMK in an accredited laboratory.

Diagram of the suitability test for the preloading (BS EN 14399-2)
Initial type tests include:
Comprehensive testing of bolting assemblies elements (screws, nuts, washers) according to the following standards:
- EN ISO 898-1: Mechanical properties of fasteners made of carbon steel and alloy steel – Part 1: Bolts, screws and studs with specified property classes – Coarse thread and fine pitch thread,
- EN ISO 898-2: Mechanical properties of fasteners made of carbon steel and alloy steel – Part 2: Nuts with specified property classes – Coarse thread and fine pitch thread,
- EN 3506-1: Mechanical properties of corrosion-resistant stainless steel fasteners – Part 1: Bolts, screws and studs (ISO 3506-1:2009),
- EN 3506-2: Mechanical properties of corrosion-resistant stainless steel fasteners – Part 2: Nuts
and bolting assemblies according to the following standards:
- EN 15048-2 Non-preloaded structural bolting assemblies – Part 2: Suitability test,
- EN 14399-2 High-strength structural bolting assemblies for preloading – Part 2: Suitability for preloading.

Screw thread failure (EN 15048-2)

Screw failure in the threaded part (EN 15048-2)