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Old October 8th, 2007, 07:14 PM   #1
nd4spd71
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Bolt strength question

I made some shackle mount brackets to go on the rear of my '86 chevy pickup that I am building for a trail rig. They are setup to use the 3 factory mounting holes for the stock rear bumper, (which has been removed) plus one more that I will have to drill. My question is will 4 - 1/2" diameter Grade 8 bolts be strong enough to hold up to the stress of pulling a full size rig out if it is stuck? Thanks in advance for your help.
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Old October 8th, 2007, 07:18 PM   #2
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yes, just make sure they are torqued properly and the holes arent oversized too much
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Old October 8th, 2007, 07:24 PM   #3
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A grade 5 will have a higher shear strength but you will be more than fine with the 8.
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Old October 8th, 2007, 07:30 PM   #4
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Quote:
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yes, just make sure they are torqued properly and the holes arent oversized too much
Where would I find the torque specs for them? If I remember right the holes are .550 so I should be good there.
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Old October 8th, 2007, 07:30 PM   #5
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A grade 5 will have a higher shear strength but you will be more than fine with the 8.
In this app. they are under tension and not in a shear load. So a 8 is great when in dought over kill.
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Old October 8th, 2007, 07:32 PM   #6
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Originally Posted by nd4spd71 View Post
Where would I find the torque specs for them? If I remember right the holes are .550 so I should be good there.
95 on NC
110 on NF
both 0.50" dia
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Old October 8th, 2007, 08:06 PM   #7
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Thanks all
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Old October 8th, 2007, 08:07 PM   #8
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In this app. they are under tension and not in a shear load. So a 8 is great when in dought over kill.
Also, I Believe that when this has been stated before, the 8's are still stronger in shear, as well.
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Old October 8th, 2007, 08:15 PM   #9
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Quote:
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Also, I Believe that when this has been stated before, the 8's are still stronger in shear, as well.
8's are stronger all around. A grade 5 will bend before it fails, where a grade 8 won't. Still there is almost no application (besides cost) that a 5 is better than an 8.

The one thing 8's have problems with is that a nick or a notch in the bolt really cut down their strength.
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Old October 8th, 2007, 08:17 PM   #10
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Also be sure to use a grade 8 lock nut not a 5 nylock like some people do.
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Old October 8th, 2007, 08:18 PM   #11
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Also, I Believe that when this has been stated before, the 8's are still stronger in shear, as well.
Yes they are. Shear is figured at 60% of it's tensile strenght.
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Old October 8th, 2007, 11:13 PM   #12
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Also be sure to use a grade 8 lock nut not a 5 nylock like some people do.
biggest mistake i see.

always make sure all your hardware matches.
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