Once I made a "hex" head bolt and nut from 2 inch brass and left it on my
desk at work as a paper weight. The bolt head was not really hex but had
seven faces rather than 6 and the thread was left-handed. Visitors would
invariably pick it up and play with it while talking or waiting for me to
get off the phone. Everyone would notice the left-hand thread, but almost
no one picked up on the seven-sided head until I asked, "Do you see anything
else strange?"

Bob Swinney
wrote in message
...
"Bryan" wrote:

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

Is there some wisdom about the history of this?

bmw

Well, an even number of sides are needed to allow for open end
wrenches leaving out 3,5,7,...

4 is the first number that works but has a fairly large diameter and
only 4 wrenching positions. Worked great for farm implements. Still
a good choice at times. Still used.

6 is next. Must have been a good compromise on diameter relative to
bolt shank, 6 wrenching positions, and works with 12pt bo and sockets
to give 12 wrenching positions.

8 would have to be closer tolerance on bolt head and wrench. Likely
would not work well with open end wrenches or polish calipers.

Wes

--
The Constitution wasn't perfect but it sure beats
what we have now.