Torque Wrench Calibration Capability: (Up To 1,100 Ft/Lbs)

The purpose of a torque wrench is to apply the correct amount of torque to tighten a fastener such as a nut, bolt or screw. Torque wrenches were originally used by municipalities to prevent over-tightening of nuts and bolts on water and steam pipes in the early 20th century. The basic design of the torque wrench has evolved greatly over the years to fit many different types of applications. The torque wrench is now a commonly used tool in industries around the world, including manufacturing, construction, maintenance, aerospace and transportation.  Controlling the accuracy of applied torque is a vital task for a wide range of processes found in industries from manufacturing to aerospace.  Companies must be assured that torque specifications are met during their manufacturing processes to ensure the quality and, most importantly, the safety of their product.  A rigid and sustained calibration program is essential to maintain this ever important goal.

There are several types of torque wrenches and each type is available in many different sizes and designed to suit a wide range of torque specifications. Click type, slip type and break type are three basic styles of torque wrenches:

• Click torque wrenches make a loud “click” noise when the specified torque is reached. Over-torque conditions are common with this style of torque wrench due to the fact that the click occurs around 3 degrees after the specified torque is reached.
• Break torque wrenches indicate the specified torque has been reached by deflecting 20-90 degrees on delivery. This limits the amount of torque applied.
• Slip torque wrenches prevent over-torque by sending a signal when specified torque is achieved and then release.

A preset torque wrench is designed to apply a single specific torque value. Some preset torque wrenches have no external scale but are internally adjustable within a specified range and come with a special tool to make the adjustment. Other preset torque wrenches, such as a T handle or T bar are more simplistic and are not adjustable. Adjustable torque wrenches have an external scale near the handle showing the available range in increments of the measuring unit such as foot lbs (ft/lbs). The handle is turned until line or arrow meets up with the desired amount of torque. Common units of measure for torque wrenches are inch pounds (in/lbs), foot pounds (ft/lbs), Newton meters (Nm), centimeters per inch (cm/in), kilogram-force per centimeter (kgf/cm) and ounces-force per inch (ozf/in).

Torque wrenches should be checked and re-calibrated often to compensate for wear or defective parts. Any adjustable torque wrench should be stored at 20% of the full scale value of the range to prevent damage to internal parts. Most manufacturers recommend calibration of a torque wrench after every 5000 cycles or 1 year. However, process accuracy requirements may dictate more frequent calibration.  A “cycle” of a torque wrench is completed each time a torque wrench is used to meet the amount of torque it has been set to.