SAE Grade-8 bolt snapped @135ft/lbs

[UnAnswerd]

Avbug,

There is no doubt that aircraft-class fasteners are superior. I never doubted that. All I'm contesting is that SAE grade-8 hardware will suffice for my particular application. Just as someone else said, I am using multiple fasteners at any given point of attachment. The failure of one fastener will not result in carnage, and the problem can be noted before the results are catastrophic.

I value your input, and trust in everything you say. But understand that I'm working on a truck suspension, not a Boeing 777 wing spar. Above all, I wouldn't do anything that might potentially become a hazard to myself or others. Trust in my judgment, and sleep at night knowing that I'm not building an airplane.

 

[Clutch_Cargo]

HOLY CR*P!!

I thought this was just about an appropriate torque value for a bolt... silly me.

cc

 

[belchfire]

Avbug,

I wish to point out to you that construction
of things like skyscrapers are engineered
and built with SAE grade hardware. So are
American cars (excepting special applications).
There are standards, the bolted joints are
designed around the limitations of the minimum
standards for the sae bolts. They are also
avalible with different kinds of corrosion
protection from none to galvanized.

Unanswered...I seem to recall something about
a suspension project some months back. You
must be getting along with it.

Did you lube the bolts/threads??? Look back
at the chart. The waxed bolts only took about
45% of the torque of the dry bolts!

Is the bolted joint properly designed? (Is it
putting the bolts in shear rather than tension).
Were you using self locking nuts? The drag on
self locking nuts changes the torque value.

Are the bolt holes round, true and properly
aligned?

I bring these things up because a poorly designed
or built joint will fail even if you use Avbug's best
NAS close-tolerance high strength bolt.

Oh yeah...try to find a retailer that can provide
US manufactured hardware. That crap that is
getting over here from the people's enslavement
camp of China is not worth a rat's a$$

 

[avbug]

The chinese and the mexican hardware seems to be the worst. A lot of our hardware is Japanese and generally that's a good product and up to snuff.

I wish to point out to you that construction
of things like skyscrapers are engineered
and built with SAE grade hardware. So are
American cars (excepting special applications).
There are standards, the bolted joints are
designed around the limitations of the minimum
standards for the sae bolts. They are also
avalible with different kinds of corrosion
protection from none to galvanized.

Actually, a lot of large consutruction is welded, and often hardware other than SAE is used. To stipulate that SAE grade is used is rather simplistic, given that 8 different grades are in use, each with very different strengths and properties.

Most American cars use metric fasteners and threads, not SAE.

While true that many joints are designed to be secured by bolts manufactured to SAE standards, the truth is that many SAE "standard" parts are very inconsistent from lot to lot, and don't hold up. I've seen more than a few twist right off on automobiles...if you've worked around cars much, you'll know this, too.

Did you lube the bolts/threads??? Look back
at the chart. The waxed bolts only took about
45% of the torque of the dry bolts!

Lube Torque is always a critical consideration in any torque application. The publications detailing the particular installation should always specify if the torques are applied wet, or dry, and generally what is to be used for the lube torque.

 

[troy]

SAE grade 8 fasteners will work great for truck suspension, It just looks like you were torquing them alittle tight. I don't think that anyone uses aircraft grade bolts on trucks. End of story, next thread?

 

[avbug]

I don't think that anyone uses aircraft grade bolts on trucks. End of story, next thread?

I do. I also use it on the lawn mower.

All that hardware that comes off the airplane has to go somewhere!

 

[troy]

Ok, I stand corrected. At least you are not buying av grade fasteners for the high performance lawn slicer!!