This Resource Centre provides general guidance only. Always follow the equipment manufacturer’s instructions, the product technical data sheet and your site’s safe system of work. Isolate stored energy before maintenance. For safety-critical, regulated or uncertain applications, ask a competent engineer or the product manufacturer to confirm the specification.
The aim of tightening is normally to create the required clamp load. Torque is only an indirect method and is strongly affected by friction.
Before tightening
- Confirm bolt, nut and washer grade and dimensions.
- Inspect threads and bearing surfaces.
- Check whether the specification assumes dry, plated, oiled or adhesive-coated threads.
- Use the specified tightening sequence and stages.
- Select a calibrated tool with a suitable working range.
Changing lubricant, coating, washer or threadlocker can change the relationship between applied torque and achieved clamp load. Do not reuse a torque value from a superficially similar joint without checking the engineering specification.
During and after tightening
Apply load smoothly. Avoid extensions or adaptors that alter tool calibration unless accounted for. Mark or record completed fasteners where the procedure requires it. For critical joints, use the specified verification and traceability process.
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