"CWLee" wrote in message ...
Can anyone here point me toward an authoritative history of
hex head nuts and bolts? I see square nuts and bolts in old
machinery and tools in museums, but I don't think I've seen
a hex head nut or bolt in anything built before 1900. Does
anyone know who invented/developed the hex head nuts and
bolts? When, where, why, etc? Any info on this topic
appreciated.

Many thanks.

Interesting question. Since I was headed to the library last night, I
thought I'd see what I could turn up. From a fastener book from about
1950, I found out that cold-heading machines were around in the 1840s,
hex nuts were being punched out of flat stock in the 1880s,
screw-making machines(not automated) were around in the mid-1800's and
they were rolling threads in the 1880s. No sign of a date for hex
head introduction, it was probably wider spread after the Bessemer
process made cheap(and uniform) mild steel available. Hand-forged
wrought iron nuts and bolts were probably easier to make with square
heads. I saw no signs of hex head bolts being milled, they weren't
made that way in quantity as far as I can see. Upsetting and forging
in a die are lots faster and cost lots less. One short article did
mention that larger hex nut stock was planed from square stock before
machining instead of starting from drawn or rolled hex stock, for
those nuts that weren't punched from flat stock.

Stan