From: James Fuerstenberg <xgg2356@dcmdc.dla.mil>
Any theories, ideas whether 1/4' allen head bolts are stronger
than grade 5 hex bolts.
I'd venture to say that wet spaghetti is stronger than grade 5 hex
bolts...
Chris K. mentioned SPS Technology and Allen, two companies which make
serious industrial fasteners. Another option is to go to aircraft
bolts. The standard AN3-AN20 series are theoretically similar to SAE
grade 5 in ultimate strength, but made to much higher standards. The
MS20004-MS20024 series is about 30% stronger in tension, with -much-
higher fatigue resistance due to careful manufacture and better thread
design. NAS624 bolts, if you can find them, are something like 50%
stronger than SAE 5.
This stuff is hard to find. If you don't happen to live near the
Boeing surplus store in Seattle, there are places that sell aircraft
fasteners by mail-order. Check the ads in Trade-A-Plane, available at
your local newsstand. Some people, but not many, have managed to
convince maintainance shops at small airports to sell them bolts for
reasonable prices.
One thing about allen head bolts is that they have very small heads.
This means that you -must- use hardened and ground washers with them.
If you use regular (or no) washers, the washer will gradually deform,
causing the bolt to lose tension and fail.
This is probably a good time to plug one of my favorite books, Carroll
Smith's "Nuts, Bolts, Fasteners, and Plumbing Handbook" (ISBN
0-87938-406-9). If you build stuff, you _need_ this book..
-john
John Wroclawski
jtw@lcs.mit.edu
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