Why are calibrated wrenches used in pretensioning high-strength bolts?

Calibrated wrenches are essential tools in pretensioning high-strength bolts because they are designed to apply a precise and consistent amount of torque. This consistency is crucial for achieving the required pretension in the bolts, which directly impacts the structural integrity of the assembly. When high-strength bolts are tensioned properly, they ensure that the connection can withstand applied loads without failure.

Using a calibrated wrench prevents variations in tightening that could lead to inadequate tensioning or over-tightening, both of which can compromise the joint's performance. Properly pretensioning bolts helps to avoid issues such as bolt slippage or relaxation over time, leading to potential structural failures. Therefore, the use of calibrated wrenches is integral to achieving the necessary and uniform tension that ensures safety and reliability in structural applications.