I have found these most helpful,
- - -
Gewinde-Normen (The Best On Threads Info)
http://www.gewinde-normen.de/en/index.html
- - -
The International Fastenings Locator 1980 (116p)
https://archive.org/details/FasteningsLocator1980
- - -
Edit-Update 07-08-2014
- - -
Bolt Science
http://www.boltscience.com/pages/screw4.htm
- - -
History of Screw Threads
http://www.sizes.com/tools/thread_history.htm
- - -
British Tools & Fasteners, LLC
http://www.britishfasteners.com/?gclid= ... fgodgokALw
or
http://www.britishfasteners.com
- - -
British Standard Whitworth (BSW)
https://en.wikipedia.org/wiki/British_S ... _Whitworth
- - -
What Is a Screw Thread?
http://www.wisegeek.com/what-is-a-screw-thread.htm
- - -
Screws, Nuts & Bolts on IndustryNet®
http://www.industrynet.com/search.asp?headers=SC0720
- - -
Sems Screw .com
http://www.semsscrew.com/
- - -
PSM i
http://www.psminternational.com/en/prod ... nload.aspx
- - -
Enjoy.
Ken.
