Ok now you got me looking. This is one of those things that won't affect the way of life as we know it but it might win you a bet sometime. The following was quoted from this link......http://www.practicalmachinist.com/vb/an ... us-113448/
03-06-2006, 01:04 AM #3 J Gull
S. E. Kansas
I did some more looking and found this @ http://www.usenews2.org/group/rec.cr...le-545754.html
Which says this
"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.
New Beginning Church