I hope that I'm not supplying the group with information that everyone
knows, but....
It's important to use SAE Grade 5 bolts and studs for almost every
automotive application. Grade 5 bolts are easily identified by 3 radial
dashes 120 degrees apart on the cap. The more dashes the stronger the bolt,
but you don't want any less than three. I'm not sure how to identify nuts
visually.
I remember a few years ago a news article about counterfeit fasteners
being a big problem. Around this time, I purchased some 5/16" bolts marked
as Grade 5 from a hardware store and they stripped when I torqued them top
50 ft-lbs.
The best place to get nuts and bolts that you can trust is a company that
sells only nuts and bolts. Every city of any size has one or more of these
stores. Next best would be to buy them from TRF or Moss.
Other "Fun Facts" on fasteners (from Shigley's Mechanical Engineering Design
3rd ed.):
..."three full threads (engaged) are all that are required to develop the
full bolt strength"
"(Bolt preload i.e. torque) may be relaxed by yielding of the clamped
material, by extrusion of pain or plating from the contact surfaces, or by
a compresion of rough surfaces. Extra contact area may be provided by
hardened washers. This is especially necessary if the bolted parts are
relatively soft and the bolt head or nut does not provide sufficient bearing
area."
Thanks,
Milo Kral
'67 MGB
'71 TR6
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