Bolts STRETCH Like Springs?

[@HacksbyDad]

Check out all of my Nuts and Bolts videos in this playlist... kzbin.info/aero/PL_WcGw5s6Cq6YK_s-NNne1838j25ijmii 👍😎

[@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.

[@HacksbyDad]

Interesting… thanks! 👍😎

[@vaguincolombia]

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

[@HacksbyDad]

You’re welcome and thank you! 👍😎

[@AlphatecEngineering]

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

[@HacksbyDad]

👍😎

[@goodun2974]

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.

[@zijie-he]

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

[@HacksbyDad]

I never thought of it that way. Thanks! 👍😎

[@zijie-he]

@@HacksbyDad 😆

[@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.

[@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.

[@azi6477]

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!

[@HacksbyDad]

👍😎

[@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)

[@wilsjane]

When you slightly stretch a bolt and it returns to its original length, you are within the first modulus of elasticity. If you stretch beyond that point, you have entered the second modulus and it will no longer return to its original length. You can easily demonstrate this using an elastic band. Stretching to the point where you feel a natural resistance is fine and the band will continue to retract. Beyond that point retraction will be considerably less and it will soon fail. Traditional spanners are are designed with a length that allows you to feel when you are coming to the end of the fist modulus.

[@izaacbanks3337]

​@@wilsjane I'm quite experienced and can normally feel that with any length tools

[@wilsjane]

@@izaacbanks3337 Exactly. But I am sure that you would automatically not use a 3 foot wrench to tighten an M6 bolt. Believe me, I have seen that one. The guy looked quite puzzled when the head snapped off. LOL

[@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.

[@HacksbyDad]

Interesting. I haven't experimented with stainless steel bolts. I did some quick research and was surprised with what I found. First, the recommended torque value for 1/2" x 13 bolts is only 45 ft-lbs. I think the recommended values are 70% of max values so the max would be only 64 ft-lbs. Second, the Milwaukee specs for their M18 impact driver state 1,700 in-lbs or 141 ft-lbs of torque. If the above are correct... it would be very easy to over-torque the 1/2" stainless steel bolts. I don't have an impact driver, so I can't do this test... yet. Maybe this video will take off and hit 50k views which should be enough to pay for the impact driver. 😎

[@markplease]

@@HacksbyDad If you’re in Southern California near me I can drop one off 😁

[@HacksbyDad]

@@markplease Thanks, but the Pacific Ocean separates us. Aloha! 🤙😎

[@ifell3]

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

[@HacksbyDad]

👍😎

[@achecase]

And that's a good thing!

[@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 :)

[@HacksbyDad]

Thanks! I’ve heard about degrees of rotation and yield bolts but have no experience with them. I’ll do more research when I the time. 👍😎

[@fookingsog]

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

[@HacksbyDad]

I think so. This bolt was a cheap grade 2. 😎

[@goodun2974]

​@@HacksbyDad, most stainless steel fasteners are pretty soft and stretchy compared to carbon steels ---- but the stainless threads sort of cold-weld to each other (can't remember the technical term for it). [It's called "galling"]

[@ollimatik]

In theory as long as the bolts are steel, different grades would stretch the same. The grade of the bolt indicates at what load (stress) the bolt will fail, but steel has the same "elasticity" (Young's modulus) regardless of strength.

[@jeffreystephenson6946]

Why