Bolted connections in structural steelwork must be tightened to the correct torque to ensure the joint performs as designed. Under-tightened bolts can slip under load, while over-tightened bolts may fail in tension. Using the wrong bolt grade, size, or tightening method compromises the structural integrity of the entire frame. This talk covers the correct bolt tightening procedures and what every steel erector needs to know.
Key Hazards
Structural connection failure from under-tightened or loose bolts
Bolt shear or tensile failure caused by over-tightening beyond specification
Wrong grade or size of bolt installed reducing joint capacity
Hand injuries from using incorrect tools or poorly maintained wrenches
Control Measures
Check that every bolt is the correct grade, size, and length as specified on the connection drawing.
Use calibrated torque wrenches set to the value specified in the structural design for each connection.
Tighten bolts in the sequence specified by the engineer, typically from the centre of the group outward.
Ensure bolt threads are clean, undamaged, and lubricated as required by the bolt manufacturer.
Carry out a visual check after tightening to confirm all nuts are fully engaged and washers are flat.
Record torque values for each connection on the bolt tightening record sheet.
Use only approved bolt assemblies — do not mix components from different manufacturers or grades.
Inspect torque wrenches for damage before use and ensure calibration certificates are current.
Report any bolt that cannot achieve the specified torque to the structural engineer before proceeding.
Remember
Every bolt must match the grade, size, and length specified on the connection drawing
Calibrated torque wrenches must be used and set to the design-specified torque value
Bolts are tightened in sequence, typically from the centre of the bolt group outward
Record torque values for every connection on the bolt tightening record sheet
Never mix bolt components from different manufacturers or different strength grades
Report any bolt that cannot reach the specified torque to the structural engineer immediately
Applicable Legislation: CDM Regulations 2015 · BS EN 1090-2 (Execution of Steel Structures) · BS EN 14399 (High Strength Bolt Assemblies) · Health and Safety at Work etc. Act 1974