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grade 5 and grade 8 bolts?

babyburb

babyburb

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I know grade 5 bolts are marked with 3 lines on top, how many lines for grade 8. I am mounting anchor hooks on the new bumper with a 12000 lb winch. I want to go to the heavier grade bolts.
thanks!
 
Typically it's 6 lines for grade 8, 3 lines for grade 5.
But not everyone adheres to the standard. Most do though.
 
yeah, most should have 6 lines on top... but not all do. You definitely want gr8. It is stronger than a 5 in every way. Don't listen to any clowns on the net who will tell you that a 5 is better at anything other than being cheaper.

j
 
The grade eight bolts have a line pointing to each corner of the bolt head. There is some other funky grade with the same amount of lines not aligned with teh corners i think......(from my engineering Design book).
 
I've seen some companies use dots instead of lines for their grade markings. Just remember that a grade 8 will have a mark of some kind at every point of the hex head.
 
not true

jekbrown said:
yeah, most should have 6 lines on top... but not all do. You definitely want gr8. It is stronger than a 5 in every way. Don't listen to any clowns on the net who will tell you that a 5 is better at anything other than being cheaper.

j
Click to expand...

a grade 8 bolt is stonger because it its harder on the Brinell Hardness scale,t herefor making it more of a crystaline stucture which is stronger in every way, except for shear loads. a grade five bolt being softer is more mallable and will strech when a side load is applied. a grade 8 will shear. thats some thing to keep in mind, it depends on application as to whether a grade 5 or 8 is better for the application. a grade 8 will shear before a 5 will. a 5 will pull apart before a grade 8 will. grade eight's strength is for clamping force, if the bolt will ever see a side load on it, a grade 5 is better. flame away , but thats how it is. some1 try and disprove me and find some evidence to support my post. not tryin to be a smart ass, but that be the truth. and tow hooks are in a shear load position with the frame, therefor a grade 5 would hold it longer before you reach a failure. any other engineer's on here, any1's dad a engineer? ask or post up
http://www.americanfastener.com/technical/grade_markings_steel.asp
heres you markings but i'll find something else to prove my point

this is a good read too http://www.americanfastener.com/technical/grade_markings_steel.asp

this too http://www.zerofast.com/torque.htm
 
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also watch where you buy your hardware. Home Depot in particular has really low quality fasteners. Produced offshore, they don't actually meet the specs for the grade they say they are.
 
in cegusman's post on page 9 its says that is a myth, but i have seen it demonstrated by a bolt manufacturer. the 8 will shear while the 5 will strech then break. the grade 8....has the composition made to shear, its so dence and hard....its kinda like a banana is soft and will flex some, dip it in some liquid nitrogen(like hardening the bolt it makes the molecules denser and align...now take it out of the nitrogen it will shatter like glass
 
use the grade 8's what i witnessed may have been set up to get my employer to spend more on bolts , because everthing i have found backs up that it is a myth, and i got taught that while going to school also, guess i learned somthing today.thats a good thing
 
So was the manufacturer trying to sell Grade 8, or Grade 5? If it was 5, I thought those were typically LESS expensive? Or was your employer looking for a bolt that would shear instead of bend?
 
And all of this isn't even half the story, you also have to have the appropriate torque. Plus fastener nuts typically side one way or the other, lubed or no lube. Bottom line, study the links.:D
 
too quote Billavista...

"...and while Grade 5 fasteners may exhibit the necessary strength in some applications, in others they do not, and the lower strength and possible misuse of them is simply not offset by the marginal cost benefit. Grade 8 bolts exhibit greater tensile, yield, and shear strength as well as greater fatigue resistance and, just as important, are capable of greater torque specs and therefore much greater pre-load and clamping strength."

the "grade 5 will bend, while grade 8 will brake" theory is bogus... that may be how they fail eventually, but under an identical load that bends a grade 5 to the point of failure, the grade 8 is still holding strong. Those charts were cool.. and in every one of them the gr8 has higher specs... :thinking:

j
 
blazin_blazer said:
a grade 8 bolt is stonger because it its harder on the Brinell Hardness scale,t herefor making it more of a crystaline stucture which is stronger in every way, except for shear loads. a grade five bolt being softer is more mallable and will strech when a side load is applied. a grade 8 will shear. thats some thing to keep in mind, it depends on application as to whether a grade 5 or 8 is better for the application. a grade 8 will shear before a 5 will. a 5 will pull apart before a grade 8 will. grade eight's strength is for clamping force, if the bolt will ever see a side load on it, a grade 5 is better. flame away , but thats how it is. some1 try and disprove me and find some evidence to support my post. not tryin to be a smart ass, but that be the truth. and tow hooks are in a shear load position with the frame, therefor a grade 5 would hold it longer before you reach a failure. any other engineer's on here, any1's dad a engineer? ask or post up
http://www.americanfastener.com/technical/grade_markings_steel.asp
heres you markings but i'll find something else to prove my point

this is a good read too http://www.americanfastener.com/technical/grade_markings_steel.asp

this too http://www.zerofast.com/torque.htm
Click to expand...

No, you are wrong. A grade 8 bolt will have a higher shear strength than the same size grade 5 bolt.

Will a grade 5 bend more than a grade 8 when exceeding their shear strength.......sometimes. If you apply "X" amount of shear force to a grade 5 it may very well bend, but apply the same "X" amount of shear force to the grade 8 bolt and nothing happens at all because you have not exceeded the shear strength of the grade 8 bolt. Keep in mind that even if the grade 5 bolt is still holding the pieces together, if it's bent then is has suffered a severe degradation in it's strength and will completely fail soon (assuming the function of the parts it is holding together have not already "failed" because the bent bolt is obviously no longer clamping the pieces together as it did originally).

Will a grade 8 usually break before bending.......probably. But part of that reason is because it requires such a high shear force to make it fail, that the force is simply high enough to shear the bolt........and of course the grade 8 is harder so it will deform less. A grade 5 bolt would of already of completely failed in shear long before reachiing the amount of shear force required to fail the grade 8.

A grade 8 bolt can bend before it breaks....I've had it happen on my truck.

FYI - I'm a mechanical engineer.........
 
yeppers... and we can't discount the higher resistance to fatigue that Grade 8 hardware has either. If a bolt is going to get loaded every single time you use your rig (suspension bolt or something), then over time the grade 5 is going to weaken/fatigue faster than a grade 8. It'd take someone with mad engineering skillz to tell us the exact effects over a specific time frame... but in any case, I plan on keeping my K5 for decades... and I don't want all my hardware snapping off 5 years from now just because I went cheap with them grade 5s.

j
 
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