Proper Uses of Torque Wrenches

A torque wrench is a device used to measure how tightly a nut or bolt is installed. If a bolt is too loose, the assembly can leak or fall apart. If a bolt is too tight, the bolt can fail or removing the bolt can be impossible.

Beam Type Torque Wrenches

Two types of torque wrenches are used: the beam type and the clicker type. The beam type looks like a ratchet handle with a numeric scale at the handle end and a pointer attached over the the socket end, pointing back to the scale. As you tighten the fastener, you bend the handle and the pointer points to the number representing the applied torque on the scale. To use a beam torque wrench, you must see the scale while you are turning the wrench.

Clicker Type Torque Wrenches

The clicker type wrench looks more like a traditional ratchet handle. At the handle end is either a knob to twist or a digital display to set the desired torque. By setting the torque on the wrench, you are setting a spring that will pop when you apply the correct torque. You tighten the fastener with steady pressure until the torque wrench clicks. You will also feel the click in the handle of the wrench. Clicker type wrenches are easier to use when you do not see the scale while tightening the fastener, but you do have to set the wrench correctly every time you use it and unset the spring when you are finished with the wrench.

When to Use a Torque Wrench

A torque wrench should be used for all critical fasteners, which are used to join two different types of metal, like a steel engine block to an aluminum head. Or use the wrench when connection failure can result in injury or death, such as for lug nuts on a car tire or the handlebar stem on a bicycle.

How Much Torque to Apply

The proper amount of torque is specified by the engineers who designed the assembly. The best source of torque specifications is the factory manual for the device being repaired. If a fastener is too loose, it can come unfastened due to vibration. If a fastener is too tight, it can strip threads in a block or nut or damage one of the parts you are trying to connect.