The first time you look at an overlocker sewing machine, it might appear there are threads running every-which-way. Overlockers are available in two-thread, three-thread and four-thread machines, with each line of thread contributing to a neatly finished seam. Change the thread spools on an overlocker before the last of the thread is removed from the spool. If the thread runs out and the end goes all the way through the machine, you will have to refer to the threading diagram when threading an overlocker.
Pull about 1 foot of thread off the thread spool on the overlocker and cut the thread right next to the spool. This is the thread you are removing, not the one you are putting on the machine.
Pull about 1 foot of thread off the end of the new thread spool. Tie the end of the thread from the old spool to the end of the thread from the new spool. Prepare all the spools on the overlock sewing machine by tying the new thread to the old thread.
Pull slowly on the end of the old thread to draw the new thread all the way through the machine, except for the needle's eye and looper's hole. Stop pulling before the knot goes through the needle's eye or looper's hole.
Look at the machine's tension guide--the dial with numbers or slash marks used to adjust the tension. Make sure the thread is seated in the tension guide. Sometime the thread will pop out of the tension guide when the knot is pulled through the dial.
Push the machine's upper thread through the needle's eye using your fingertips. Hold the thread end, for the looper thread, with the pointed-tip tweezers and feed the thread end through the looper's hole. It will be very hard to feed the thread into the looper's hole if you do not use tweezers because there is no room for fingers in the looper area.
Follow the coded thread chart printed on the overlocker or in the owner's manual if the machine is not threaded when you begin.
If your overlock machine has a coded threading system, refer to that instead of the owner's manual when threading.