According to Bryan :
Whilst thinking about another problem, I find myself wondering, "why is
it that bolts have hex heads rather than octagonal or some other
number?"

Well ... for a few guesses:


1) Hex has more surface area on the flats, and is harder to round
off with a wrench.

2) Hex uses less material relative to the major diameter than
octagonal.

3) Hex stock stores more compactly. No waste space.

4) It takes fewer cuts to machine the flats, if not working
from stock already that shape. This saves machining time.

5) Hex is easy to grip with a three-jaw chuck, which is the best
for quick gripping of round stock. Octagonal would require a
universal 4-jaw -- which does exist, but which is uncommon, and
a slight irregularity with 4 jaws means that one will not be
gripping firmly.

Is there some wisdom about the history of this?

I'll leave others to deal with the history. I've just listed
the advantages to hex which come to mind readily. Besides -- it is time
to go to bed. :-)

Enjoy,
DoN.
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