Torque Knowledge

What is Torque?

Torque is a measure of the rotational force applied to an object around an axis or a pivot point. It's commonly associated with the turning or twisting force that causes an object to rotate. Mathematically, torque is calculated as the product of the force applied and the distance from the axis of rotation to the point where the force is exerted. It's often expressed in units such as Newton-meters (Nm) or foot-pounds (ft-lb).

In practical terms, torque is essential in various fields, especially in mechanics and engineering, where it's crucial for tightening bolts, nuts, and fasteners to specific levels to ensure proper assembly and functionality of machinery and structures. Torque is also fundamental in understanding how forces act upon rotating objects, such as engines, motors, gears, and other mechanical systems.

Breakaway Torque

Breakaway torque, also known as residual torque, refers to the force required to initiate movement in a previously tightened fastener. It represents the clamp load or tightness of the fastener in a joint. When measuring residual torque, tools assess the torque needed to transition a static fastener to a dynamic state, overcoming the friction that holds it in place.

Tools measuring residual torque detect the peak torque just before the fastener starts moving and note the subsequent torque drop. There are two methods for measuring residual torque: one involves setting zero degrees as the target angle to capture the torque drop when the fastener begins to move, while the other sets a specific degree of rotation, typically 3 degrees, to record the torque value at that point.

The accuracy of residual torque measurements hinges on appropriate parameter settings. Skilled operators might use a zero-degree target angle, while less experienced ones may opt for the 3-degree rotation setting. These measurements are crucial for auditing previously tightened fasteners to ensure compliance with torque specifications.

The appropriate direction to apply force to establish breakaway torque is crucial—typically in the same direction the fastener was initially tightened.

It's crucial not to loosen the fastener during the breakaway torque measurement, as doing so alters the joint's condition, undermining the accuracy of the audit. Instead, tightening the fastener to capture the moment of movement provides a more precise breakaway torque reading without compromising the joint.

Residual torque, also known as breakaway torque, refers to the amount of force required to initiate motion in a previously tightened or static fastener. When a fastener, such as a bolt or a nut, is tightened and then subsequently left in a static state without any additional force applied, residual torque measures the force necessary to break the static friction and set the fastener in motion again.

This measurement is crucial for understanding the level of clamp load or tension that remains in the joint after the initial tightening process. Residual torque indicates the tightness or retention of a fastener within the assembly and is often used during quality audits or inspections to ensure that fasteners maintain their intended level of tightness over time.

Tools designed to measure residual torque detect and record the peak torque just before the fastener begins to move and may note any subsequent torque drop. The accurate assessment of residual torque helps determine whether a fastener has loosened or relaxed from its initially tightened state and provides insights into the integrity of the joint or assembly.

In summary, residual torque is the force required to overcome static friction and initiate movement in a previously tightened fastener, serving as a crucial metric for assessing the retained tension in a joint.