When we say self threading we are usually talking about different things. What is important to me is the fact that my new Bernina serger is much easier to guide the thread through the places where each thread has to go. My first simplier machine would drive me crazy if I accidently let one of the "loopers" run out of thread. It required unthreading all four spools and starting over in a specific sequence or it wouldn't work at all. My newer machine lets you just reroute and thread the one thread that has run out or broken without having to start from scratch. I usually just tie on when I want to change colors.