USING AN ADAPTER WITH A TORQUE WRENCH
Figure 1
If an adapter is attached to the drive of a torque wrench, the wrench will not give actual torque
indicated by the setting of the handle. A simple formula however, allows you to figure out what the setting should be to deliver a predetermined amount of torque at the end of any adapter to the fastener.
The following letters are defined as:
A= Length of the torque wrench when set at the middle scale setting (inches).
B= Length of adapter (inches from center hex bolt to center of torque wrench square shaft.
C= Desired torque at end of extrusion
D= Setting for accuracy within + or - 6%.
Here is a typical problem. You have an adapter that adds 10.0 inches to a torque wrench length (dimension B) What should the setting be to obtain 320 ft. lbs. of torque at the end of the adapter.
A= 22.57 inches (length from adapter mounting point torque wrench to center of grip / handle)
B= 10.0 inches (Length from adapter mounting point of torque wrench to center of hex slot).
C= 320 ft. lbs. torque (desired torque at end of extension).
D= Unknown (setting you need to set torque wrench to = 320 ft. lbs for accuracy).
| (A) | (22.57) | (22.57) |
C = | |||
| (A + B) | (22.57 + 10.0) | (32.57) |
Your Answer (D) is a setting of 222 ft. lbs. on the torque wrench will give 320 ft. lbs. of torque at the bolt. By using the above formula an accuracy of + or - 6 % of the desired torque will result at the end of the adapter due to length change during grip adjustment.
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