This is one of those How-It's-Made factory tour films, which shows how guitar strings are made in the D'Addario factory. It also shows the quality control procedures used to test that the strings are fit for their purpose. The strings are stretched and twisted in a medieval torture chamber until they break. I never knew there was such a thing as a ball-end-sorter. Even though its mostly mechanised, a human worker still has to start the wire wrapping process on each string by hand. And the final coiling, before they are put in bags, is also done by hand

http://www.youtube.com/watch?v=8U-vZLZKgJc