Gma-n-Gpa, the best way I know to answer your question is as follows. Torque is usually express in pound-feet. That is, 1 pound-foot is the rotational force exerted on a bolt when 1 pound of force is applied at exactly 1 foot from the bolt, with the wrench at right angle to the rotation. If you double the distance from the force to the bolt, but exert the same 1 pound of force, then you double the torque (1 pound of force at 2 feet will be equal to two pound-feet ). On a calibrated torque wrench of the beam type (old school), the slender beam does not move with relation to the bolt, but the large arm flexes, and is calibrated to give an accurate reading on the scale based on the amount of flex due to force exerted. The key here is that the degree of flex is precisely calibrated for the exact length of the arm. If you add length to the handle, the flex changes, increasing with longer extensions, and the calibration is no longer accurate. Think of it this way (exaggerated) - if you put an extension 20 feet long on the torque wrench, you could probably move it with one finger, but the flex would be tremendous, and would likely not move the bolt at all. So you would be exerting a large force, but the reading would be at or near zero. Hope this helps explain "my opinion".
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