Originally Posted by Gleniveve

Most often it is the top thread that is causing the problem. When the thread is made it has to be
twisted or it would all unravel. As the thread is coming off the reel to sew it is twisting more as you
go along and that interacts with the bobbin thread and it gets knotted from the twisting. If you
take the reel of thread off the top and turn it over (top to bottom) it will untwist itself.
So, whenever it starts to play up just turn the reel of thread over. Magic happens. It is all in the
way the thread is made because it has to have that twist in it to stay together. If you are using
an industrial machine it happens even faster because it can be sewing at 6000 to 8000 stitches
per minute. It really is Magic. lol Gleniveve