I've used two threads in one needle. Have done it successfully two different ways. The first and easiest way was I just took the two threads and treated them as one. Worked fine. I also did it placing one thread on one side of the upper tension disc and one thread on the other side of the upper tension disc. That also worked fine. I couldn't see any difference between the two, so now I just treat the two threads as one. I did not have any shedding. What I used it for was for doing black buttonhole stitching on appliques, so I was going pretty slowly.