There are several tightening strategies used for bolted joints in the industry, such as torque control, angle control, yield control, and stretch control. The most common strategy is torque control due to the ease of use, simple tooling, and availability of tabulated torque and average corresponding clamp force values for common fastener sizes and classes.
For some special applications, angle controlled tightening strategy is used where maximum fastener strength utilization and more consistent clamp load are required. Unlike torque control tightening strategy, angle control tightening is more complicated and requires more advanced tooling. In addition, there are no tabulated values that provide the angle control tightening parameters for a specific fastener material and size. The tightening specification is rather developed on a case by case basis.
This paper provides a method for developing tightening specification for angle control tightening. It also provides a method to calculate the maximum expected final torque which can be used to select the proper tool size. The maximum expected final torques are tabulated in the paper for most commonly used fasteners. Finally, the paper provides a criterion for detecting parts and/or joint quality issues when angle control tightening is used.
