Mr. Sandman
So. Cal
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Joined: 04/24/2006
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An excellent and easy to understand read on grade 5 & 8 bolts. I'll be checking and probably replacing mine prior to my next trip.
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lancer360
Charlotte, NC
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Bolts are a specialty of mine. There is a big misconception regarding lock washers. In studies, lock washers have been proven to be completely ineffective when used with hardened bolts such as grade 5 or grade 8. The split ring lock washer is designed to bite into the metal of the nut and the mating material. The bolts are so hard though that the lock washers can't get a bite. Another big problem with split ring lock washers is that there is no standard for their manufacture that I have even been able to find. So you can end up with a nice hardened steel bolt and a lock washer that is no better than a piece of weak junk steel. So when you clamp down on the bolt the proper amount, the lock washer just deforms and squashes. Over time the lock washer will continue to creep under the bolt forces and eventually can compress to the point that the bolt looses tension and can break.
The best defense against bolts coming loose is to have a properly designed joint (i.e. only hardened flat washers, no lock washers) and to properly install the bolt (i.e. turn the nut not the bolt when tightening) to obtain the necessary clamping force. The best secondary defense is a thread locker compound such as Loc-tite. If you plan on removing the bolt in the future I would recommend that you only use a medium strength compound. The high strength works so well, that generally the only way to get the bolt loose is to heat it up above 450F to get the threadlocker compound to break down or cut the bolt off.
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BigJon05
Ripon
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Joined: 02/08/2005
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I have something similar happen with the leaf spring bolts - I had all of the hardware replaced and afte the fist trip out 3 bolts had the nut completely back off, 1 of them had no nut! So they re-tightened everything and I have yet to take a big trip and am worried about it happening again. I will check them every trip but am wondering if I should use locktite on them?
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pupeperson
Silver Springs, NV
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My question regards the number of the bolts. The OP said "Four of the six bolts..." broke or bent. The pin box was held on with only 6 bolts? That would be 3 on each side. Mine has twelve 1/2" fine threaded bolts that are grade 8, six on each side. I would think that ten or twelve bolts total would be far more common than six.
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Broccoli1
Los Angeles
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Joined: 02/28/2007
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More Bolt info 
Bolt Science
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DuneMe
Elk Grove, CA
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Joined: 09/19/2004
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I checked my trailer. I have I think 8 larger Grade 5 bolts on mine. I then went over to my buds trailer at the storage yard and he has like you about 12 smaller Grade 8 bolts.
His is a couple years older so, it looks like they went from more smaller higher grade bolts to fewer larger lower grade bolts in the more recent models.
I have no idea which way is best but, I'll be keeping an eye on mine.
pupeperson wrote:My question regards the number of the bolts. The OP said "Four of the six bolts..." broke or bent. The pin box was held on with only 6 bolts? That would be 3 on each side. Mine has twelve 1/2" fine threaded bolts that are grade 8, six on each side. I would think that ten or twelve bolts total would be far more common than six.
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Albin
North Alabama
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JSGrewal wrote:I read somewhere recently that grade 5 may be better in a shearing application because they tend to bend before breaking whereas grade 8s will sheer off. Not sure how true it is, but it may be worth looking into. I know I will check my bolts!
I wish this old wives tale would die a much needed death.
Billavista' Fastener Tech article
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Racorman
Santa Cruz, California
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Joined: 12/15/2003
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4 THE TOYZ wrote:My buddy and I both own 2009 Weekend Warrior 5th wheels (I know, I know). Anyway, last weekend in Pismo, the bolts in his pin box snapped. Four of the six bolts completely snapped in half as we were pulling in the sand. No major damage as we caught it in time.
My question is, why would they not use Grade 8 bolts?? The bolts that were on his and are on mine don't even look like a hardend bolt. It seems ridiculous they would not use grade 8. Any thoughts...
Photos would be great......
I just checked mine and all 12 bolts are #8. Six on each side.
You only had a total of 6 bolts?
AKA..... 56Nomad
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Steve76eb
Folsom, Ca
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Albin wrote:JSGrewal wrote:I read somewhere recently that grade 5 may be better in a shearing application because they tend to bend before breaking whereas grade 8s will sheer off. Not sure how true it is, but it may be worth looking into. I know I will check my bolts!
I wish this old wives tale would die a much needed death.
Billavista' Fastener Tech article
You should see all the people over there that take everything he writes for gospel. LOL
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Albin
North Alabama
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Steve76eb wrote:Albin wrote:JSGrewal wrote:I read somewhere recently that grade 5 may be better in a shearing application because they tend to bend before breaking whereas grade 8s will sheer off. Not sure how true it is, but it may be worth looking into. I know I will check my bolts!
I wish this old wives tale would die a much needed death.
Billavista' Fastener Tech article
You should see all the people over there that take everything he writes for gospel. LOL
And on this issue, they should. Read Lancer360's response, the Rockcrawler article and the FAQ at the Bolt Science link, they agree almost word for word.
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