Bolts STRETCH Like Springs?

Did you know that metal bolts stretch like springs? Learn what I found out in this experiment.

@HacksbyDad

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[urieaaron]

In Lansing Michigan's GM motor plant, we used this property in taming the Quad 4 engine . Because of the dissimilar metal and their expansion rates, the engine used to chew up its head seals. There were a lot of things they did to fix this, but one was lengthening the head bolts and letting them act as springs to help take the pressure and wear off the seal.

[vaguincolombia]

Simple, interesting and straight to the point. Thank you papá.

[jhonbus]

Cool demonstration. This is essential for bolts to work as fasteners at all! The nut stretches the bolt and the tension in the stretched bolt provides the clamping force. If there was no stretch, the only way to generate clamping force would be to constantly apply torque to the nut.

[AlphatecEngineering]

Looking for a video like this for years, love it 💚💯🔥

[goodun]

A good example of stretchy bolts is when the same bolts that hold a heavy transformer to a guitar amp chassis are also used to bolt a ground terminal to the chassis: they always come loose due to a combination of spaker vibration, transport vibration, bolt stretch, and material compression. Always. Modern electrical codes require a separate, dedicated earth ground point, not shared with any other ground nor any mechanical connection.

[ytdeagle]

Would be interesting compare stretch of clean dry bolts to fully oiled bolts.
Torqued to the same ft/lbs to demonstrate why bolt torque is for clean dry bolts in general.
If you torque lubed bolts they will be over stretched and closer to yield point.

[markplease]

Ok, this is awesome. Would you consider showing what happens when the bolt is severely over torqued by a brushless Milwaukee impact? The theory is that it will yield and you will lose that spring effect, which causes a lot of losses on the power grid (due to over torqued electric connections)

[TwoWheeledPotato]

stretch bolts exist for certain things so this isn't a surprise to me but measuring by torque isn't the standard way, usually it's by the degrees of rotation. presumably a 1/4th or 1/2 a thread (90 to 180 degrees) is a certian amount of stretch. anyway, great video :)

[zijie-he]

bolt and nut is a pair of very long ramps which facing each other and being pushed together very hard.

[ifell]

Torque to yield 😅 they have a certain amount of elasticity up until the yield point.

[markplease]

The bolts used on the powergrid are 1/2” stainless with two flat washers and a split lock washer. It would be so awesome to validate the theory that Milwaukee impacts wreck the bolts via over torquing them.

[azi]

Scientifically I appreciate you using the metric system, better not mix up with imperial. The USA already lost a space shuttle because of mixing both systems!

[fookingsog]

Would different "Grades" of steel have different amounts of "stretch"???