The Bridgeport milling machine is an interesting case in the history of technology. The design was settled upon in the late 1930s and hasn't changed a great deal since. Virtually every vertical milling machine made since has been an interpretation of the Bridgeport design. The term "Bridgeport" is often used to mean vertical milling machines generally, a la "Kleenex". Other types of machine tools, e.g. lathes and drill presses, are significantly more diverse; there are larger differences between manufacturers and over time. Welding machines are far more diverse. But vertical milling machines are all, at heart, Bridgeports.
Though the Bridgeport design was popular in the 30s, its history is deeply intertwined with the World War II production effort. Adaptable precision production of precision parts was needed, especially for aircraft manufacture. Today, computer-controlled machining would have been an obvious choice, but automated manufacturing was barely in its infancy at the time. The solution was to buy Bridgeport mills, one for each machining operation, such as milling a slot. The part would be moved down the line from one machine to the next, one operation per machine. When time came for a new run of parts, the machines could be set up anew in fairly short order. This strategy worked well, but required the manufacture of thousands of machines.
After the war, these machines flooded the used market. Many have been re-sold over and over. Milling machines generally, and well-made examples especially, are highly durable. Many of the milling machines I've used up and down the east coast have been WWII-era machines. Some are in remarkably good condition, especially for industrial equipment older than my parents.
The Bridgeport mill is an appropriate technology, an essential tool for the small metal shop. Yet these machines were created to make killing machines. Such has been the case with machine tools since their earliest days. As L.T.C. Rolt wrote in discussing machine tools of the 1700s, "It is precisely because armament production has always been so uninhibited that the industry has contributed so much to the general progress of technology. Though we have not yet acquired the wisdom to convert one into the other, by producing better swords we certainly learn how to make better ploughshares."
Rolt, L.T.C. (1965), A Short History of Machine Tools, Cambridge, Massachusetts, USA: MIT Press
"Indeed, it is no exaggeration to say that much U.S. plant capacity to this day, and even some of the machine
tools in use, originated in this period [1941-5]."
Carlsson, Bo, The development and use of machine tools in historical perspective, Journal of Economic Behavior & Organization, Volume 5, Issue 1, March 1984, Pages 91-114http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V8F-45GSDTT-8&_user=634929&_coverDate=03%2F31%2F1984&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1260645813&_rerunOrigin=google&_acct=C000033778&_version=1&_urlVersion=0&_userid=634929&md5=a79a3fbaed643da3ecdb44ff8f256db1