Just saw a number about tool calibration that really got my attention

I was reading through an old FAA advisory circular, the one about precision measuring equipment, and it mentioned something I never really thought about. It said a torque wrench that's just 4% out of spec can cause a bolt to be under-torqued by over 15% in some setups. I mean, we check our tools, but idk, that gap between the tool error and the actual bolt load surprised me. I found it because I was looking up rules for our shop's audit next month. It made me pull every torque wrench off the line yesterday and send them out, even the ones that weren't due for six months. Maybe it's just me, but that feels like a tiny error with a big real world effect. Has anyone else run into a small calibration slip causing a bigger issue than they expected?

3 comments

3 Comments

mia_hart901d ago

Ever feel like your torque wrench is playing a prank on you? I once spent an hour chasing a "loose" bolt only to find out my wrench was just lying (and not even by that much).

daniel_wood2d ago

Yeah, that 4% to 15% jump is the math working on an angled adapter or an extension. The error multiplies. We had a guy using a crowfoot on a tight access bolt, and the calibration was barely out. By the time you factor in the extra leverage from the adapter, the actual torque on the bolt head was way off. It's why the manual always says to re-check the setting if you add any kind of cheater.

morgan8982d ago

That's a solid point about the math, but honestly, the manual's re-check rule feels like a band-aid. If the calibration is even a little off to start, you're just building error on error. Saw a tech snap a bolt on a water pump because his adapter was at a weird angle and he just added a few pounds to the wrench setting. The real fix is getting the tool right before you even reach for the cheater bar.