Sq. Head Bolt Grade

[BackBay]

I went to www.fastenal.com to order new squarehead bolts for the front and rear rims of a SA. What grade of bolt is required? The choices were: 2, 5, 8, A, and A307A.

 

[JT]

I would buy a minimum of grade 8, don't know what the letters mean, though.

 

[ScottyHOMeY]

I'd tend toward a 5. 2 could be too soft and might deform/bend too easily. 8 might be so hard/brittle as to break under stress. 5 strikes me as the practical compromise.

 

[Dave_Id]

I think originally Class 2 were used, because I don't ever remember seeing any lines on the heads, but they have a tendency to stretch, so I too would go with Class 5. Class 8 would be aircraft grade.

 

[Haas]

I would go with the grade 5. Grade 2 is too soft and I don't think the Grade 8 is needed for this application. I don't think IH used grade 2 bolts for rim bolts. The originals are IH bolts so they would not necessarily have the same markings as the present standards. I don't know what the letter designations mean, but I suspect it is a bolt for structural applications like fastening structural steel in buildings.

 

[BackBay]

The orginial bolts were deformed so whatever strength they were was not sufficient.

Although, after 58 years, I may be deformed a bit too.

 

[ScottyHOMeY]

Yep!

I think that's what those of us saying Grade 5 are agreeing on.

If you think about it, those eight bolts have to take a lateral stress from all the power you put to the ground. They need to be strong enough but have some give. Too soft, they bend. Too hard they snap.

2 would likely be too soft, 8 too hard, and 5 just (or just about) right. Kinda (but not just exactly) like Goldilocks and her porridge

 

[dave guest]

I replaced the hex heads on my A. Machine shop sold me no grade bolts. They said with 5/8, I think it was, that would be sufficient. Two years ago, still holding. They are square heads and look original.