Without getting too complicated, torque is a measurement of the force used to tighten Fasteners such as Hex Bolts, Hex Head Cap Screws and other Nuts and Bolts. This applies to bolts, screws and nuts. But the exact torque or force used to tighten any given fastener is a complicated question and it is difficult to come up with a straightforward answer.

When you apply force to fasteners (commonly referred to as torque) it will inevitably put stress on the fastener in some way. Often the material or coating will stretch, strain or become compressed. When the incorrect amount of torque is used it can (and often does) result in fastener failure.

So how can you avoid this situation?

In order to avoid dangerous situations, many engineering specifications will state the torque required. Maintenance and assembly workers need to pay attention to these specifications and use only the amount of torque stated by the designers or manufacturers.

It is important to note that most often an acceptable torque range will be stated. That means you can use any torque value within those limitations and still be assured of stability. These figures are calculated by taking the type of fastener into account, as well as the size, grade and thread of the product.

Coatings and lubrication are also important factors. The torque values should state whether any lubrication can be used and applications that deviate from this will require another calculation. Different coatings also change the accepted torque – so don’t expect to use the same force on an untreated bolt as you would on a galvanized product.

Always keep in mind that the torque applied to the fasteners will also have an effect on the fitting. You need to be sure that the torque used will not result in damage to the fitting materials. Splitting, cracking and weakening are all common results of too much torque. Plastics and other soft materials are often at risk of these conditions.

Anyone dealing with fasteners on a regular basis should use a top quality torque wrench to ensure accuracy. These tools allow for the application of exact levels of torque and will help to avoid fastener failure and fitting damage in many cases.