Grade 8 Bolts In Tool Box

[b.j.oneill]

I Guess I need to put better bolts in my tool box was practicing 4wd launches and broke the bolt on the passenger side slid about 6" It was sure fun though glad I didn't lose the whole box. Oo. Oo. Anybody else find this out the hard way?

 

[BK]

What grade bolts were holding it down?



from some past experience... not a tool box, but somewhat related. I was missing hardware on a hitch I needed to install from Reese. I called them and spoke with one of their apps people. I noticed all the hardware was grade 6, not 8. He said the Reese recommends grade 6 for the hitches since grade 6 is not as brittle as grade 8. Even though grade 8 will handle a greater static load and higher torque, it will not handle the shock that the grade 6 hardware can. They said the grade six is more than strong enough for the hitches.



Anyway. . Reese just sent me a whole new hardware bag.

 

[illflem]

BK, is right, grade 8 isn't the strongest in shear type situations because it's too brittle. Always best to use the same grade that was there before.

 

[b.j.oneill]

I was just kiding about puting grade 8 in it just had some little dinky bolts that came with it i'm just going to put regular bolts in maby a little biger probably 1/4in that it is intresting to know about the bolts though I was wondering why my hitch never came with grade 8

 

[Cooker]

I'm glad I read this. I was going to replace the grade 5 bolts in my hitch with grade 8's. The are sitting on the bench awaiting install.



Does anybody have a chart that list the strength of the different grades of bolts?

 

[BK]

here's a good chart:



http://www.bychoice.com/mechanical.htm#TORQUE_DESIGN_CONSIDERATIONS



Scroll down a bit from where the link brings you to find the torque spec chart based on bolt size Vs Grade bolt.

 

[MDKram]

Beware of counterfit fasteners made offshore which may be "brittle" as they may not use the proper metallurgy to achieve the desired strength. Properly made Grade 8 bolts are not inferior to Grade 5 or 6 in shear. All have very similar ductility and toughness characteristics. Rockwell C hardness does not differ much, % elongation is very close... Grade 8 has more area under the stress strain curve which translates to greater ability to absorb energy. Grade 8 bolts (A490) are used in fatigue and impact applications all the time in structures (bolted connections and pins). If you need higher shear strength, pay more and buy Grade 8, if a Grade 5 or 5. 2, or 6 will suffice, then save your money!



As an aside, I believe the bolts holding the bumper brackets to the frame on our trucks are Grade 10. 9 (metric designation) which translates to Grade 8 mechanical properties.