I finally learned what a torque wrench extension does to readings

Was working on a 737 flap track at Hartsfield-Jackson last Friday and an old-timer saw me using a crows foot on my torque wrench. He said I was messing up my numbers by not accounting for the offset distance. Did the math with his formula and I was overtorquing by almost 10 ft-lbs on a 150 in-lb job. Has anyone else been doing this wrong for years without realizing it?

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hugo6453mo ago

You know, I've been thinking about that "offset distance" thing and it's not just the crows foot. The angle you hold the whole setup at matters too. If you're not perfectly 90 degrees to the bolt axis, you're adding a cosine error on top of the extension math. I'm not sure why nobody talks about that part of it, but it can throw things off by a few percent on top of everything else.

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paul_lane803mo ago

Wait, are you saying I've been unknowingly adding a sneaky cosine error to my torque readings this whole time? (That would explain a lot, honestly - my last project had some fasteners that just felt "off" and I couldn't figure out why.) I'm the guy who's always fiddling with the crows foot angle, thinking I'm being super precise, and then I realize I'm holding the whole setup at a weird tilt because my workbench is slightly uneven. Between that and my shaky hands, it's a miracle anything I build stays together. Maybe I should just stick to using a regular wrench and guessing, haha - probably about as accurate as my "carefully calculated" approach anyway.

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