I'd like to add a comment or two to this thread, if I may. Bolts can be
subjected to two different types of stress -- shear and tension. If the bolt
is ONLY subjected to shear stress, then the type of nut used is immaterial.
In this application, the only purpose served by the nut is to keep the bolt
from falling out.
OTOH, if the bolt is subjected to tension loads, then the nut is just as
important as the bolt.
Quite often, bolts are subjected to both type of stress at the same time, but
usually one is much more severe than the other. The bolts holding the upper
ball joint on the front suspension of a TR6, for example, is primarily loaded
in shear, with a much lesser tension loading. The bolts holding the lower A-
arm brackets to the frame are loaded mostly in tension, with much less shear
Good engineering practice dictates that bolts be loaded in shear if at all
possible, rather than tension. For severe loads, it is recomended that the
bolts be loaded in double shear.
Never-the-less, grade five nuts are so cheap there is no reason to buy
anything less, then you only have to worry about the specialized application
that calls for grade 8. Which means that you DON'T buy nuts and bolts from
Home Depot for use in your car. The bolts sold there (except those in
specially marked packages) are of such a low grade that they will stretch
before the correct torque value is reached!
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
'74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
'68 MGBGT---organ donor for the '74