wnjj wrote:
Maybe it's the potential to end up with the head of the torque wrench not directly above the bolt, particularly with a long extension. Or using your hand to support the extension adds a slight amount if drag.
Edit: Either way, it's not enough to matter.
This is the issue. An extension that is not held directly in line with the bolt changes the fulcrum length (longer or shorter) and makes the wrench handle's calculated torque length no longer valid. The amount of angle that you would typically see is going to be minor, but still affects the torque value imparted to the bolt, so the myth is correct. Something to be aware of when using a torque wrench, but for the average DIYer, not a lot of difference.
