School me on bolt grades....

[TheBeast_88K5]

I was in class yesterday, and the instructor was giving a lecture on 'direct replacement' and why you do it....


I had NO idea that a grade-8 bolt had LESS shear strength, but more longitudinal strength...


Is this true?

And why>?

 

[Deuling]

That would have to do with the makup of the metal. The more carbon in them will make them harder, but more carbon equals more brital, less carbon equals more ductile. And you spelled school wrong

 

[Smokinthehippies]

if i remember correclty,
they say grade 5 will bend before failing completely which keeps you from having a major catastrophe.
but i'm pretty sure that idea was scrapped because they showed while grade 8 is more likely to snap at failure point, its failure point is X amount greater than grade 5 that it is a moot point.


http://www.rockcrawler.com/techreports/fasteners/index.asp
science wins again. he has a good write up on here.

 

[dremu]

That would have to do with the makup of the metal. The more carbon in them will make them harder, but more carbon equals more brital, less carbon equals more ductile. And you spelled school wrong

Because they teach "makup" and "brital" in skool. I'm just sayin'.

All I know is grade 5 and 8 ... well, I've occasionally used like grade 2 carriage bolts, which are stupid soft, so I just over-size them and don't torque on 'em too hard.

Should you ever have the need to grind or drill on them -- making leaf spring center pins, say -- you'll find that grade 8 fasteners are harder than grade 5's, but as mentioned, more brittle. The 5's are easier to work but will deform more easily under stress.

Whether this is important will depend on how they are used (i.e. will they see stretching, or shear force), proper sizing, and whether Muddin' Manny installed them

[For the n00b's, Muddin' Manny is an ex-member who would go into excruciating detail in his writeups, and IIRC used grade 8 in everything "because it is better" and would include half-true technical nonsense to that effect. Every time.]

-- A

 

[dremu]

I had NO idea that a grade-8 bolt had LESS shear strength, but more longitudinal strength...

More brittle means you could shatter it with a sideways chisel, say -- compare a brick to, I donno, cheese. The brick is brittle, will shatter, vs the cheese just deforms. ("Chiseling cheese" sounds like a euphemism for a sex act, possibly including Jell-O and small scaly animals.)

However, the same brittle-ness means it's stiffer, which isn't the right technical word but is good for the layman. Assuming the same materials were threaded, you can see where the brick would hold a nut in place on the thread were you to pull it along the long axis ... versus cheese would again deform.

(Now, how the hell you run a die down a cheese rod, I'm unclear ... but I hope the analogy helps.)

-- A

 

[Deuling]

Hey at least brital and makup sound the same as the correct spelling. Not like shool and school lol.

 

[shady]

so from this I'm gathering, Grade 8 would be better for a head bolt style of application and the grade 5 would be better in the leaf spring/shackle bolt type area.

 

[dremu]

Hey at least brital and makup sound the same as the correct spelling. Not like shool and school lol.

Shure it is. Shool rhymes with shedule.

-- A

 

[NorCal_Chris]

so from this I'm gathering, Grade 8 would be better for a head bolt style of application and the grade 5 would be better in the leaf spring/shackle bolt type area.

Kinda, But like was said the grade 8s are miles stronger than the grade 5 even after it deforms so it is a wash. Just grade 8 it

 

[Fordum]

For the n00b's, Muddin' Manny is an ex-member who would go into excruciating detail in his writeups, and IIRC used grade 8 in everything "because it is better" and would include half-true technical nonsense to that effect. Every time.

Hey, I resemble that remark.........
I even tend to use 8s where less strong bolts would do.
I broke down and bought a big assortment one time, and got it in grade 8 even though 5 would have been cheaper and done 90% of what I needed.

As for less sheer strength and more longitudinal strength for a grade 8,................Well, if the question comes up on a test, say yes. That is what he is expecting to see.
If you are building something in the real world, the answer is no.

Cool, I went looking for the specs on the different fasteners so I could plug them into the formulas and prove it, and found this site.

http://www.rockcrawler.com/techreports/fasteners/index.asp

Not only did he write up what I was going to, along with nice charts, but now I don't have to write up the excruciating details........

 

[shady]

I use grade 5 for everything generally. I was able to reuse my spring bolts on my burb so didnt think of it then. motor bolts and such are always bought from a kit so I KNOW they are right. Just never had heard that about the grade 5/8 differences. Good info.

 

[NorCal_Chris]

Not the best pic... But when i moved my front hangars for the 52 swap i used grade 5 bolts.
This happend. 5 of the bolts sheared off. Top one was bent and was only thing holding my bracket on.


Ironically this is the same spot that Mike broke his frame/tcase mount. Except he went to the right of this rock hole.

 

[TheBeast_88K5]

That would have to do with the makup of the metal. The more carbon in them will make them harder, but more carbon equals more brital, less carbon equals more ductile. And you spelled school wrong

Oh, okay...


and, I fixed it.

 

[TheBeast_88K5]

Shure it is. Shool rhymes with shedule.

-- A

You're the only one that works w/ 'other side of the pond'ers....'

To us 'Merican's, that's just nonsense.

 

[TheBeast_88K5]

And, thanks for all the help guys...


I'm sure I'll ask 400 more random questions like that.

 

[sweetk30]

Not the best pic... But when i moved my front hangars for the 52 swap i used grade 5 bolts.
This happend. 5 of the bolts sheared off. Top one was bent and was only thing holding my bracket on.

thats why all suspension bolts and replacements for hangers are grd 8 and fyi the rivits are bigger than 3/8th and smaller than 7/16th so besty to drill out and go 7/16th bolt size and i also get them long with a bit of smooth shanke and hardened washers and metel crimp nuts no nylock or lock washers thay fail faster.

you dont fill the hole or fill it with threads it gives it room to walk around and fail xx times faster.

 

[dremu]

You're the only one that works w/ 'other side of the pond'ers....'

To us 'Merican's, that's just nonsense.

Since when is Canada on the other side of a pond? Of course they say proe-cess and not praw-cess too =))

The one that stumped me was conTROVersy (as opposed to the Ammurican CONtroversy.)

-- A

 

[dremu]

thats why all suspension bolts and replacements for hangers are grd 8 and fyi the rivits are bigger than 3/8th and smaller than 7/16th so besty to drill out and go 7/16th bolt size and i also get them long with a bit of smooth shanke and hardened washers and metel crimp nuts no nylock or lock washers thay fail faster.

Nylock I can see failing, hate those things... but even hardened lock washers, i.e. grade 8 or the like, you see them fail?

-- A

 

[rampage]

. . .("Chiseling cheese" sounds like a euphemism for a sex act, possibly including Jell-O and small scaly animals.)

Thank you for making coffee come out my nose.

And everything after that seemed like a euphemism too. You put my mind in the gutter and it never came out again.

 

[TheBeast_88K5]

Since when is Canada on the other side of a pond? Of course they say proe-cess and not praw-cess too =))

The one that stumped me was conTROVersy (as opposed to the Ammurican CONtroversy.)

-- A

Oh... My mistake.

I thought it was Brit's, not Canadian's...