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Comment by dmkolobov | Hacker News Reader

I was one of the folks who put together the steel for a waterslide in a certain amusement park in California. Our method consisting of putting a mark across the bolt and nut after tightening it all the way down with a spud wrench, and then using a breaker bar until the mark on the nut was at the 4 o'clock position( or maybe it was 8, I don't recall ).

The inspectors would then use a telescope to check every mark. Completely blew my mind that they relied on this method, rather than something that measured the force directly.

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or you could use a drone with a sufficiently zoomed in and stabilized camera.

Totally, but the crazy part is that there is nothing preventing you from making these marks without following the appropriate tightening procedure. When the project is several months late and people are working 16 hour days, the temptation to cut corners is high.

> making these marks without following the appropriate tightening procedure

If you didn't torque the bolt tight enough then it will come loose sooner, and the lines won't line up. I'm sure there are situations where the torque of the bolt is critical for handling peak load on the system, but for a lot of situations where a torque wrench keeps you from damaging by over-tightening, and makes sure you got it tight enough that it stays tight.

I should say there's one other failure mode a torque wrench can test that that the paint doesn't by itself, and that's a failing bolt. If you've ever seen a broken bolt, and the entire surface isn't uniformly shiny, then you've seen a bolt that cracked a long time ago and then failed recently. That crack is going to show up as less torque. So if the bolt hasn't spun but the torque has dropped, you might have a problem, rather than having a freak incident where the nut spun exactly 360° since you checked it last.

I could see an argument for using paint and smartbolts for fasteners with epic failure modes, like people dying or generators exploding.

Is it standard for there to be a follow-up bolt inspection some time after the initial assembly? This was a one-time gig for us, as we were welders by trade and boss-man got the contract from a family friend, so I'm not familiar with inspection standards.

For what it's worth, we tightened all the bolts down according to the procedure, despite pressure from boss-man to do otherwise for a few of them.

I haven't wrenched professionally for anything bigger than a bicycle, and in that case one of the most expensive components (labor and parts) can be damaged immediately by too much torque or over time by not enough, so you did not want to do that without a torque wrench. Or at least not until you had muscle memory for what 'enough' felt like.

On bikes, car repair and a few other items, mine and others, I've seen sheared off bolts. In at least two of those I was involved with the tightening prior to failure, and the lightbulb moment where we figured out why the sequence of events made sense.

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