What is Torque?

What is Torque?

Torque is the rotational force that causes objects to rotate about an axis. When tightening bolts, the pushing or pulling force an operator exerts on the wrench results in a torque in the fastener. The magnitude of this resultant torque can be calculated as the force applied by the operator multiplied by the length of the wrench. From this equation, we can see that torque can be increased either by increasing the force applied by the operator, or by adding leverage by increasing the length of the torque wrench.

Torque Tensioning

When we torque bolts, we are typically clamping one of more parts together. The clamping force that holds these parts together is achieved by imparting tension within the bolt. This tensile force in a tightened fastener is common referred to as preload. When we tighten the head of a bolt down, we are converting the torque through the threads into a preload that stretches the bolt along its axis. In this regard, bolts can be thought of as very stiff springs. And much like a spring, a bolt can be stretched to a limit and still return to its original length. Engineers use this behavior to carefully select the correct number of bolts, their size and material to achieve and maintain the required clamping force in a given application through the effects of external loads, heat and vibration.

Similar to how using a longer wrench increases the torque an operator can apply on a bolt, a torque multiplier utilizes the mechanical advantage of gear reduction to apply even higher levels of torque given the same operator input. In these types of systems, the input torque is multiplied by the final gear reduction ratio to calculate the output torque. Many torque multipliers utilize a planetary style gear train with one or more reduction stages to achieve high levels of torque multiplication in a small package. Torque multipliers are advantageous in applications with high torque requirements and limited access for long, traditional torque wrenches.

Torque multipliers allow for a reduction in the lever length and operator effort.”

U.S. Patent Nos. 8,434,389 & 8,991,284

European Patent No. 2396147 