Torque wrenches have built-in devices (i.e. dials or clicks) which indicate to a mechanic when the desired torque

limit has been reached. However, when adapters or extensions are used on the torque wrench that increase the

length of the wrench, the torque applied will be greater than the dial reading, or preset torque limit.

Some quick mathematics will help the mechanic decide what the dial reading or preset torque limit should be to

obtain the desired torque limit when an adapter or extension is used.

First, measure the length of the extension from the center of the connecting point with the torque wrench to the center

of the socket.

For example:

A 6 inch extension is used on 18 inch torque wrench. The torque desired on the screw is 300 ft-lb (407 N·m). Using

the formula, the dial indicator reading or clicker setting can be determined.

5400

18 x 300

=

=

225 ft-lb (305 N·m)

18 + 6

24

Therefore, a dial indicator reading of 225 ft-lb (305 N·m), or a clicker setting of the same level will result in the desired

torque of 300 ft-lb (407 N·m) being applied.

In most cases, adapters that add 1 inch (2.5 cm) or less to the torque wrench length do not require recalculating

torque. Only if the desired torque has an exceedingly tight tolerance should the new torque be calculated.

Be careful when deciding the length of the adapter.

In the example above, the extension will not affect the torque reading.

M0471105