Page 510
APPENDIX
TORQUE WRENCH USE
When tightening a fastener, it is important to use
a steady pull on the torque wrench. Only in this
way can accurate torque values be achieved. If
the torque value required cannot be obtained with
the existing torque wrench, a longer wrench
should be used. Dial indicator-type torque
wrenches can be used accurately when an
extension is added to the handle to gain more
leverage. With most click-type torque wrenches,
however, accuracy can be obtained only if the
point of pull remains at the center of the hand grip
area. Therefore, no handle extension can be
used with most click-type torque wrenches,
unless the tool is designed and calibrated for this
purpose.
Using an Adapter in Combination
with a Torque Wrench
It is sometimes necessary to use an adapter at
the drive end of a torque wrench. When an
adapter is attached to the square drive end of a
dial indicator-type torque wrench, the dial reading
(compared to the actual torque applied) will be
affected if the leverage length of the torque
wrench is increased. A correction factor is then
needed to achieve an accurate dial reading.
In the example that follows, a torque wrench with
a working length of 20 inches and an adapter with
a working length of 2 inches are used in
combination. The correction factor is obtained as
follows:
1. Divide total length “A” by torque wrench
length “B”.
Example:
— Total Length A = 20 in.
— Torque Wrench Length B = 18 in.
—A ÷ B = 20 in. ÷ 18 in. = 1.1 (Quotient)
589
Figure 589 — Torque Wrench with Adapter
A. Total Length (Torque Wrench Plus Adapter) B. Torque Wrench Length
5-111.bk Page 510 Monday, July 10, 2006 2:26 PM
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