Bolts- Have you seen this?

[RaisedByWolves]

So, a torque indicator...

Kinda.

You have seen those arrows on truck lug nuts that indicate visually if a lug nut is coming loose?

Think of this like those without the truck involved.

I would venture to say amusement rides and industrial applications where you would do a daily/weekly visual check of equipment by maintenance types.

 

[whitmore]

Cute item; looks like the indication depends on the threaded element stretching, pulling
a bright-red piston affixed to the tip away from the bolt head, and infilling of the space
between the piston and the window with an opaque fluid.

That implies that the indication can go wrong if you over-torque the bolt. But, it
will correctly indicate (corrosion or fracture) failure of the 'nut' at a later date.

 

[RJSakowski]

Commercial aircraft come to mind. I have read an accident report where an engine cowling came off because the fasteners had not been tightened properly.. It flew off during takeoff and damaged one of the control surfaces. Fortunately, the plane was able to return to the airport and safely land. Had it happened at 30,000 ft., it could have been a terrible tragedy.

 

[ozzie46]

That company has a video on why torque wrenches are inconsistent.

Of course they do. LOL

 

[Jake M]

So, a torque indicator...

No. Torque is irrelevant to bolts and joints. But torque is the most approachable and practical way to estimate that, so it's used very extensively. But it has too many variables for some applications. Those bolts have an elongation indicator. They literally and exactly measure the elongation of the fastener. With consistent and known materials and manufacturing, that will be a VERY accurate measure of tension, which equates literally and exactly to the actual clamp load of the joint being fastened. That, the clamp load, is the end goal of ANY torquing or tensioning process.

 

[Jake M]

Kinda.

You have seen those arrows on truck lug nuts that indicate visually if a lug nut is coming loose?

Those are a joke, invented by people in office chairs, probably insurance companies, to keep people happy who have no idea what happens when a wheel comes loose. If in fact "most" of the nuts are correct, then one or two finger tight nuts won't come loose. If there's enough relative motion between the wheel and the hub to loosen any bolts, the wheel will be off before anyone sees. And in practice, truck wheel nuts (and lugs) are A, just about universal, and B, the joint is VERY well understood and VERY over secured, and is stronger than anything that's going to happen to it. The wheel it's self will fail first. Or the hub will fail first. Most times when a wheel comes off of a truck, the nuts never moved at all, but they were overtightened, just barely into yield, too many times. Big ugga duggas are great at doing that. They keep tightening until the bolt (stud) starts to twist up. The threads on the bolt/nut have reached "self locking", where you want them, and they start to twist the bolt (stud). When the ugga dugga "hits", they turn to the right, and between hits, they spring back. That's where the ugga dugga stops. A couple of rounds of that, and the studs will literally be damaged to the point that they, and not the nuts are what fails. The telltales never move until they tumble down the road, still on their nut, with the outside end of the stud still inside of them.

There are other applications in industry where the over designed joint (safety factor) is not nearly as robust as it is in truck wheel nuts and studs, but these are not regulated in the same way, and inspections can be (reasonably) done on a given schedule, and it "should" be fine that way. That's what these self indicating fasteners are made for. Things where the operator actually could "beat something loose" if they set their mind to it. By being a stretch indicator, these bolts do not care one way or the other if the bolt's metal is stretching more (most likely) or the thing is vibrating loose (less likely). If you have a joint where there is relative motion under the fasteners..... Yeah, that's how bolts turn themselves loose, but you also have a poorly made joint at that point that needs some re-engineering.

 

[OTmachine]

That would be cool on structural bolts like swing bearing bolts on cranes. They are a pain in the butt to retorque.

And when the house comes loose, do you think the company is going to warranty them and the damage they cost? I will stick with the torque wrench.

 

[Jake M]

Of course they do. LOL

I won't disagree with the convenience of that, but the torque/tension relationship is fuzzy at best. Good enough for a lot of things, very approachable with (relatively) cheap tooling, easy instructions, and it's a LOT easier than making EVERY fastener available at each end, and with a datum surface (that can't be damaged) at each end to physically measure the actual stretch. Which of course, in the field, has to be determined for each and every fastener, not just size and pitch. This (relatively) high inaccuracy is why you see (or at least the mechanical trades see) more and more things going to torque to yield fasteners. They're designed longer than needed, with long, precise reduced section, and instead of torque to tight, you torque to some very low torque (minimizing inaccuracies of torquing) and then they're tightened by degrees of rotation, so that the stretch can be calculated at the engineering stage, and presented as a simple angle in degrees. That's not really what these do. (but the inaccuracy of torqing things is convenient, and it's faults well known... Convenient. These really don't tell you when they're tight. You still have to torque them initially, and when you remove the drive tool, you'll see the indication (or lack thereof). They don't tell you when to stop. They tell you when to come back and find out what went wrong.

 

[ChazzC]

Commercial aircraft come to mind. I have read an accident report where an engine cowling came off because the fasteners had not been tightened properly.. It flew off during takeoff and damaged one of the control surfaces. Fortunately, the plane was able to return to the airport and safely land. Had it happened at 30,000 ft., it could have been a terrible tragedy.

Although the company website notes that the inventor was involved with aviation, I didn’t see any offerings of flat head fasteners which would be used for cowlings. Frame and landing gear fasteners would probably fall within the sizes listed, as would very large structures (the largest anchor bolts I’ve seen in single-story - 50’ clear - warehouses were ~1-1/2”, and these were 20” square tube columns).

 

[7milesup]

And when the house comes loose, do you think the company is going to warranty them and the damage they cost? I will stick with the torque wrench.

Did you read Jake's posts?
So when your torque wrench does not correctly torque the fastener, will you cover the cost when the house comes loose? (whatever that means).

Many of these types of products are engineered for specific tasks requiring precision, not for the average Joe mechanic attaching a widget to a whatever.