FASTENER IDENTIFICATION - Continued
How Adapters Affect Torque Limits
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.
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.
18 x 300
225 ft-lb (305 N·m)
18 + 6
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.
Fastener Symbol Markings.