Here are web forums where you can "chat" with other machinists on topics of current interest and do a little networking.
The following are some of the many professional associations for those employed in PMT fields.
Open Educational Resources (OER) are free online materials that anyone can access anytime.
U.S. Army. (1919). Earn while you learn Wanted machinists [Recruitment Poster] Library of Congress. https://www.loc.gov/pictures/item/00651600/