What are 12.9 fasters used for?

What type of applications call for grade 12.9 fasters? Please give specific answers if you have them.

:::Edit:::
Not strictly asking about Tacomas, or even automotive.

 

Grade/Class Strength
Metric Class 8.8 Similar to Grade 5.
Metric Class 10.9 Similar to Grade 8.
Metric Class 12.9 The highest metric class for strength, it exceeds Grade 8.

 

Yes but what are the applications?

 

Sorry, I misread your question. I'm not an engineer so I cannot answer.

 

I don’t think there’s anything on a taco that would benefit from a 12.9... except maybe perhaps shock bolts, as it would perhaps have more abrasion/wear resistance, and bolt is short enough that the brittleness of a harder bolt shouldn’t be a factor. For other suspension components, a bolt with a little more “stretch” to it for clamping force or give is ideal (class 8.8). Same with aftermarket bumpers and recovery points as well, considering they could be subjected to heavy shock loads during a recovery.

In other words, I guess I’m also not sure what the ideal applications for a 12.9 are?

 

I suspect there isn't anything on the tacoma that calls for 12.9 but what about other things?

 

Head bolts are typically a 12.9/G9.

 

Probably used a lot in aircraft applications i imagine.

I think the leaf spring bolts are stronger than grade 8. Same with the big bolts at the lower knuckle in the front. The ball-joint stud material has that darker look that sets it apart from grade 8

 

If there is a demand They will be made and sold.

Sometimes the only reason they are used is the salesperson talked the customer into buying them

They were the only size bolts in the bin that would work the right length or right diameter

 

Darker look? That's not how you identify a 12.9 grade hex cap screw. The grade is always stamped on the head, whether SAE or Metric.

 

Higher grade bolt means moar ugga duggas..


Actually refers to the tensile strength of the steel the bolt is made out of. Higher grade = higher tensile strength = more axial load (tension) that the bolt support

 

Bed bolts could be that strong

 

You're right.

 

No, 12.9 grade bolts do have industrial applications. 8.8 and 10.9 are more common grades in bolt bins.

 

Im aware of the stamp on the head.

Also notice i used words like probably and I think

I handle a lot of bolts on cars on a daily basis. Not all bolts have a designation stamped on the head. The ones that come already installed on cars don't always have a stamp. Alot of torx and hex fasteners dont have any room on the head for a stamp.

When you buy a nut/bolt selection from a parts store, those will often be stamped

Generally speaking darker fasteners will be found on suspension applications where tensile strength is needed. At a glance they look different than the bright shiny grade 8s that are found elsewhere

 

10.9 and 12.9 bolts can suffer from a somewhat unique failure mode called "Hydrogen Embrittlement" Most common in poorly coated (electropated) high grade fasteners.

-molecular structure related failures due to crystalline metal. Fascinating stuff for material science geeks.


I've heard that 12.9 suspension bolts that are over-torqued (typically with a shop monkey and an impact gun) will cause these fasteners to break very quickly.



https://www.boltscience.com/pages/t...is-not-necessarily-the-case-for-fasteners.pdf

 

Connecting rod bolts, head bolts, brake caliper assembly bolts... basically allows the designer to use a smaller bolt for any given load, with all the caveats mentioned above (needs precision torquing or better yet a stretch gauge, increased likelihood of hydrogen embrittlement and/or stress corrosion cracking).

Me? I use either Toyota OEM bolts or stainless bolts from the hardware store - not as strong as SAE grade 8 or metric 10.9 when new, but will be stronger after a couple of salty winters...

 

I don’t think I’ve ever seen a 12.9 bolt used on small aircraft. However, I worked on chinooks for a while and even though they’re an SAE, I think there’s some bolts that may be similar grade to 12.9 for transmission mounts.

As for a more consistent application, maybe big rigs, tractors, etc. large machinery would be my guess for a normal usage of them.

 

Want to see really high-end fasteners in automotive use? https://www.summitracing.com/parts/arp-247-4205

They're expensive because the material is inconel 625.

 

SAE fasteners (bolts in this case) will have radial marks on the head to indicate Grade. 3 marks (spaced at 120 degree) indicate a Grade 5 bolts. 5 marks (spaced at 72 degrees) indicate Grade 8. No marks indicate Grade 2, IMHO these are best left in the bin.

Metrics are marked with the Grade number. 8.8, 10.9, 12.9

The Grade indicates the strength of the bolt. The high strength bolts require heat treatment to build the Carbon/steel structure.

Torx and Socket heads are typically at a Grade 5 strength.

The "black" treatment can come from several sources. Black Oxide, Heat treatment, anti-rust....... the color is not a reliable indicator of the bolt strength.

Yes, Hydrogen embrittlement can be an issue. The H2 invades the carbon/iron matrix to begin fractures.

FWIW, all metal is a crystalline structure.