Hello,
I am new here. I was searching for a copy of "Instructions for using and adjusting Singer sewing machine 31-15"
Singer took down the parts.singerco.com page that used to have a lot of the manuals. I contacted Singer and they directed me to http://vintagesingerparts.com for manuals, but Vintage only has the parts manuals.
The Smithsonian library has a Trade Literature collection with a sewing machine section (https://library.si.edu/trade-literature) They had a pdf of the plain user manual (http://www.sil.si.edu/DigitalCollections/Trade-Literature/Sewing-Machines/pdf/sil10-202.pdf) They list the adjusting manual, but don't have a web or pdf copy. I filled out a form, and the archive center housing the item did send a pdf of the manual, it has the adjustment pages that the plain user manual does not (PM me if you would like a copy). Smithsonian may have other brands of manuals as well, I did not check
My husband suggested using the wayback machine to find old cached versions of the Singer webpage. It works! And http://web.archive.org/web/20180727063340/http://parts.singerco.com/IPinstManuals/ should get you there. This is a link to the version of the page July of 2018. Different dates may have different lists, I haven't checked that yet. My plan is to try and download all of the manuals I can find in case the archive also goes away.
Hope this helps others find free manuals!
I have a 111W155 that we just got set up, a 211G151 that I have been using for regular sewing since the 80s, a 211W151 from my Grandma, the 31-15 from my uncle, and some other machine heads that are not set up.
My dad was a machine tech in the luggage and garment industry in the 50s, 60s, 70s. so he supplied all of the machines. I have some other non Singer heads and parts that came to me when dad passed.
Reeniebeany