Andrews Fasteners Bolt Length Calculator for BS EN 14399 High-strength structural bolting assemblies for preloading (System HR)
HR Bolt to EN 14399-3:2015 / HR Countersunk bolt EN 14399-7:2018
This calculator is for guidance only. It calculates the minimum recommended bolt length considering the maximum allowed thickness of the assembly components and steelwork.
This information is provided in good faith and is for your guidance only. Andrews Fasteners Limited cannot accept any liability for actions taken by third parties based on this information.
HR Bolt Length Calculator
Version: JS/1.02.210721.14399.2015
While the information is provided in good faith, Andrews Fasteners Ltd accepts no responsibility or liability for errors or inaccuracies in the information, or for any reliance placed on it by the user.
Nut used in calculation refer to EN 14399-3 / EN 14399-7 (HR Nut)
Washer refer to EN 14399-5 (4) (washer under the nut) or EN 14399-6 (4) (chamfered washer under bolt head) - Hardness 300-370 HV
NFW (2) refers to Nut Face Washer EN 14399-9 (Hard washer) - Hardness 38-45 HRC
BFW (2) refers to Bolt Face Washer EN 14399-9 (Hard washer) - Hardness 38-45 HRC
DTI (1) refers to Direct Tension Indicators Washer EN 14399-9 - Hardness max. 380 HV - maximum height including protrusions (3).
Steelwork thickness refers to the combined thickness of steel elements being bolted together. It’s important to include a minimum of 1 thread protruding beyond the face of the unloaded nut on the assembly. If additional plates are needed, such as for oversized holes, their thickness should be added to the total steelwork thickness.
Don’t know which components to use on HR assembly?
For calculation of thread lengths refer to:
- Thread Length Calculator for HR Bolts to EN 14399-3
- Thread Length Calculator for HR Countersunk Bolts to EN 14399-7