aoncurly |
11-16-2019 11:33 AM |
There are many factors which affect torque values in bolts - faying surfaces oily or not, material and bolt properties being clamped, temperature, washers, number of washers, gasketing material, etc. Torquing is really a measure of the clamping force of the bolt being tightened, or tension in the bolt. My point in this is that any torque wrench is only as good as the last time it was calibrated and that torqued values can vary wildly.
As an engineer, I used to get in arguments all the time with ironworkers who used torque wrenches to torque structural building bolts. Building codes require a certain minimum tension value in the shank of a bolt, not a torque. This is the most accurate way to ensure a specific minimum clamping force. This is done by calibrating torque wrenches (sometimes daily) with a device that measures clamping force. In my experience, this value would vary by as much as 15%. One day it might be 200 ft-pounds for a certain bolt size, and the next day it might be 220 ft-pounds using the same torque wrench.
I am not advocating buying a cheap or expensive torque wrench. But I think pricing may depend more on longevity (or quality) of the tool, accuracy tolerances, and the tool maintaining a calibrated amount.
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