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| Grade 8's will always be better in a situation where the bolt isn't modified. Case in point is some wheel weight adapters that required welding a bolt to the adapter the weight hangs on. A grade 8 will fail at the weld almost every time even with 7018 rod. The welding makes them brittle. Use the grade fives and increase the bolt size to largest usable.
Also remember that a grade 8 fails easier whenever it is in a situation that it can be flexed. I know the above article explains that the strength differences are greater with grade 8 but that doesn't hold up to real life farmer stuff where the bolt is in a cantilever situation and for whatever reason isn't 100% tight. The grade 5 will flex more cycles where you may catch it but the grade 8 will snap off without warning most times.
Over the years I am real careful where I use grade 8 and will most times build with larger grade 5 to equal what I would get with the smaller grade 8 bolt in the same situation. I know it doesn't make sense with the grade 8 being tougher but it's safer because of the way grade 8 bolts fail.
Edited by Dan_Lyman_NE 2/20/2010 17:46
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bolt engineer info request
