[Ian]

Chris,

I sent off an email to Larrin Thomas, as you suggested. What a nice guy! He sent me a prompt reply which is copied below.

Hi Ian,

Finding steel history can be surprisingly difficult, and 5160 is not one I have looked into. I was unable to find the history of 5160. However, I looked some at some of SAE journals from the early 20th century and found a couple things. I found a reference to 5165 steel in the 1913 journal: https://babel.hathitrust.org/cgi/pt?...ew=1up&seq=638

5165 was not present in the 1912 SAE transactions: https://babel.hathitrust.org/cgi/pt?...iew=1up&seq=51

The chromium limits of 5165 were changed in 1919: https://babel.hathitrust.org/cgi/pt?...iew=1up&seq=14

However, 5165 was removed from the SAE specifications in 1922 "as there is apparently no use for it, and 5150 has been added for shafting material and for gear purposes." https://babel.hathitrust.org/cgi/pt?...ew=1up&seq=218

I found an ad from United Steel in 1919 advertising for "spring steel" which had four different brands including "Crucia" a Chrome-Carbon steel. https://babel.hathitrust.org/cgi/pt?...iew=1up&seq=88

So I didn't find 5160 but early versions of the steel date back to at least 1913. Perhaps with this starting point you can find something.

Larrin

And a further follow-up reply ...

Ian,

I found a reference to 5160 in a 1952 book, though it doesn't talk about 5160 as being the most common choice for springs, just one of the choices. https://babel.hathitrust.org/cgi/pt?...ew=1up&seq=483

Larrin