Craftsman 320.27990 Operator's Manual page 14

After fastening, always check the torque with a torque wrench. The fastening
torque is affected by a wide variety of factors, including the following:
• Voltage
o A voltage reduction will cause a reduction in the fastening torque.
• Socket
o Failure to use the correct size socket will cause a reduction in the fastening
torque.
o A worn socket (wear on the hex end or square end) will cause a reduction
in the fastening torque.
Bolt
o Although the torque coefficient and the class of bolt may be the same, the
proper fastening torque will differ according to the diameter of the bolt.
o Even if the diameters of bolts are the same, the proper fastening torque
will differ according to the torque coefficient, the class of bolt and the bolt
length.
The use of a universal joint or an extension bar (both available separately) will
reduce the fastening force of the impact wrench somewhat. Compensate by
fastening for a longer period of time.
The manner of holding the tool or the material to be fastened will affect the
torque.
27990 ManuaLRevised_10 1202 Page 14