Proto torque adapters are designed
with a center-to-center dimension of 2". This means that the
distance from the center of the square drive of the mating torque
wrench to the center of the fasteners is exactly 2". This constant
dimension serves to simplify the process of calculating the torque
The steps as required to calculate torque when
using a Proto torque adapter are as follows:
- Determine the amount of torque required to
properly set the fastener.
- Determine the length of the torque wrench
from the center of the grip to the center of the square drive
(remember that this changes as you adjust the torque wrench
- Multiply the amount of torque you are trying
to apply (1) by the length of the torque wrench from (2) above.
- Add 2" for the torque adapter length
- Divide the result from (3) by the result from
(4). The result is the torque wrench setting required to properly
torque the fastener.
For example, you want to torque
a grade 8 fastener with a thread diameter of 3/8" and a hex
size of 9/16", using a Proto 6006AB torque wrench.
- From the Standard Torque Value Chart the recommended
bolt torque is 47 foot-pounds.
- The 6006AB torque wrench dimension is 10".
- The torque, 47 foot-pounds, multiplied by
the length of 10 inches is 470.
- Adding 2" for the torque adapter to the
torque wrench length of 10" equals 12".
- Dividing 470 by 12 results in a torque wrench
setting of 39 foot-pounds. This will result in the desired 47
foot-pounds at the fastener.
Following this procedure results in an
accuracy of ±2% (added to the accuracy of the torque wrench
it becomes W6% total). For greater accuracy, another iteration
can be performed using a measurement of the torque wrench from
the center of the grip (set at 39 foot-pounds) to the center of
the square drive.