Thread designation

[Skillet]

Can anyone tell me how the designation came about, like the 4 in 4-40 or 10 in 10-24?

Thanks,

Skillet

[BigDaddyG]

Skillet,
The history goes back (1800's) to the British. I believe it was the Whitworth standard that started it all. That standard migrated to a British standard (maybe some of the folks across the pond can chime in here). That British standard was the basis for what has become our (our being the US standard of fine and course thread as we now know it) sometime in the early 1900's as we started to standardize sizes. If I am not mistaken they have a history that tracks back directly to the British Standard.

A very interesting question, one that I will be doing some research on, but would very much like to hear what others know.

Regards,
Glen

[BigDaddyG]

Skillet,
In 1884, the British Association for the Advancement of Science started a standard that became the BA Series or Standard (Based on Whitworth and inspired by the Swiss Small Screw Thread System). In 1906 the USA wanted to adapt a Standard of there own. The Unions at the time did not want to have outside compitition and pushed for the Standard we now know. But the size denotes history are directly related to the BA Series.

I just asked an Engineer I work with (a few years older than myself...not that he was around back then) and he explained that the thread size and shape are indeed simular, but the forming was the difference. It goes back to a history of the BA standard, with some differences enought to keep shipments of there #0,#2,#6 etc from coming into the USA. But the history and the numerical carry-over are indeed connected. We were much more of a "Pat Buchanan" type of mentality back then and protecting American Jobs and especially American Union Jobs was of top priority in the country at the time.

Kudo's on the question. I can't wait to hear some other feedback on this one.

Regards,
Glen

[Skillet]

I appreciate the help! I've been looking through some old handbooks, but have not been able to find the origin of those designations.

Skillet

[sol]

interesting link
http://www.team.net/sol/tech/whitworth-hist.html

sol (no relation to Scions of Lucas)