At 09:22 AM 1/3/99 -0800, you wrote:
...
>Jim, I've been told by my engineering friends that all you need to achieve
>the maximum strength of the bolt is a thread depth equal to the diameter of
>the bolt. Now, I feel better having a bit more than this, but it doesn't
>seem likely that drilling out the nuts to achieve yet another 1/4" is going
>to add any strength. It does, however, insure that you neither bottom out
>because of too long studs, or hydraulically jam the nut if you apply grease
>to the threads (a no-no with closed end nuts).
>
>Again I say, for all the work required to replace the studs of either
>diameter, the choice is really pretty arbitrary. If one chooses 7/16", then
>use at least grade 8 or ARP super bolts and be extra careful not to
>over-torque them. With either 1/2" or 7/16", a major point is to get the
>interference fit between the knurled portion of the shank and the hub holes
>sufficiently tight. This might be harder to achieve if you replace with
>7/16" studs.
>Bob
For those who might be interested, I have a hardened tool steel fixture to
drill and tap either front or rear hubs for 1/2-20 threads. The fixture
locates on the proper hub steps for concentricity and fits over a remaining
7/16 stud for rotational location. After drilling and tapping, I use
1/2-20 button head socket screws which are typically in the grade 8-9
strength range. They are available in several appropriate lengths to
accommodate various wheel thickness and/or spacer plates. I install them
with hi strength locktite, but they remain changeable. This seems to be an
essentially bullet proof method to install changeable high strength studs
for severe duty and avoids the problems of knurl fitting, location,
alignment, and hydraulic press requirements.
I also strongly recommend that any closed mag type nuts be "chased" with
the appropriate bottoming tap to produce full depth threads. Most
manufacturers of these type of nuts do a very quick and dirty threading
operation leaving 1/4" or more untapped at the bottom. This is just a
"good practice" procedure to avoid potential problems.
Tom
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