How to use a torque wrench
How to use a torque wrench
This video from Norbar Torque Tools, the world's torque specialists, takes
you through the best practice use of a Norbar Torque Wrench.
The most common wrench is called a click wrench. It will indicate by a
mechanical mechanism when a pre-set torque has been reached. The pre-set
value can be set by the user, or by a Quality Control Department. The
second most common torque wrench is used to check an already tightened
It can have a mechanical or electronic sensing mechanism and can display by
means of an electronic or analogue display. There are other tools referred
to as "torque wrenches". These are powered by pressurised oil or air and
are known as hydraulic or pneumatic torque wrenches. The use of these
devices is more complex and will be covered in a later article.
Most torque wrenches are used for tightening nuts and bolts accurately
although there are also some other uses. These other uses will be discussed
in another article. There are two main reasons why we use a torque wrench.
One reason is to achieve the correct level of tightness. The bolt needs to
be stretched to create a clamping force on the assembly. If the torque
value is too low, the assembly will not be secure. If the torque is too
high, the bolt may break. The torque wrench allows the operator to tighten
the bolt as the designer intended.
The other reason to use a torque wrench is to be consistent on every bolt
in the assembly. Used properly the torque wrench will ensure that all bolts
have the same torque applied.
The effect of badly tightened bolts can be seen in lost time, money and
lives. A machine stops working and takes weeks to repair. A bridge
collapses. A wheel comes free from a truck and hits a car travelling in the
other direction. Good quality torque wrenches do save time, money and
The largest part of the uncertainty comes from the operator. Problems will
arise if the torque value cannot be set correctly. Unfortunately many
wrenches have a scale that is difficult to read, or becomes worn away with
use. It can also be difficult to position the cursor accurately. Some
wrenches have a vernier scale to help. These will only work with one set of
units. Be sure whether the vernier is designed for the N.m, kgf.m or lbf.ft
The operator will also affect the torque by using the wrench too fast. The
"click" wrench is designed to give a physical signal when the desired
torque is reached. If the wrench is operated too quickly, the torque will
go too high before the operator can stop.
With dial or electronic indicating wrenches, the operator must be able to
see the dial or display. This can be difficult in applications where there
is poor light or limited access. Finally the operator must apply a smooth
and slow force at 90 degrees to the wrench. Side loads can alter the torque
applied and may cause the wrench to slip off the bolt.
There are many different styles and qualities of torque wrench available.
With the correct selection, operation and maintenance, a torque wrench can
save you time and money. To make the correct decisions you may need to seek
the advice of specialist torque tool provider like Norbar Torque Tools.
Further information on the use of Norbar's products can be obtained from
our website, from the literature supplied with them and by contacting
Norbar or our distributors.