Before air threaded machines my mother used to tie the new thread onto the end of the old thread. Unfortunately she didn't live to see air threaded machines. I traded her serger in for an 8 thread air serger, BabyLock of course. I don't have any problem threading it but when I took my class on how to operate it the teacher said to hold the thread about an inch or so from the end, give the end a little tug to make it straight and then place that inch of thread into the hole, but she also demonstrated how to use the threading tool. If you don't have one I'm sure the BabyLock dealer has them for sale.