Tutotial: threading the sewing machine for sewing with a twin needle or double needle. You will need to keep your needle threads separated in 3 places (if possible. this is how my machine is and many others, but you may want to look in your machine’s manual for specifics for your machine).
1. The threads must unwind in opposite directions to keep them separate, 1 will unwind clockwise and the other unwinding counter-clockwise. The first spool, shown on the left below, will unwind over the top to the left side.
The second spool, shown on the right side, will unwind over the top to the right side.
2. The threads should be kept separate in the tension disk. There is usually a divider piece inside the tension disk, to create an inner and an outer path within the tension disk. It’s hard to get a photo of this, but you can see the thin metal piece sticking up in the pic below (click on photo for a larger, close-up view). This divider keeps the two threads separate, yet still fed through the tension disk. Make sure your presser foot is up while threading your threads through the tension disk.
You can test whether you’ve got the threads on separate tracks by pulling on one and looking to see if the other thread moves. When done properly, the second thread should not move or wiggle when the first thread is pulled through the tension disk.
3. The thread guide just above needles
Thread first spool completely, then thread the second. The first spool should be threaded through the inside track of the tension disk, and through the last thread guide (just above the needle). The second spool will then be threaded through the outer track of the tension disk, and will not be threaded through the last thread guide. Bobbin has no special instructions. After threaded, I am able to place the first spool back down into sewing position, to help keep the threads from touching.
Remember not to back stitch when using a twin needle, for most often the needle will break. Instead sew past the place where you began sewing.
For more tips on how to sew with a twin needle, see this post.