The Singer Sewing Machine Co. began production of the Singer model 15-91 sewing machine in the 1930s. It was the first model of sewing machine produced by Singer that came in only an electric model; consumers could not order it with a treadle (the manual operating pedal on older models). It is a straight-stitch machine with backstitching capability. It was a popular model, and Singer produced it up until the mid 1950s. The Singer model 15-91 was manufactured only in the United States.
Insert the needle into the machine. Raise the needle bar and loosen the thumb screw. With the needle positioned sharp-end down, turn the needle to where the flat side is facing left and insert it into the hole in the bottom of the needle bar. Tighten the thumb screw to secure the needle.
Secure the thread spool to the machine. There is a hole on either base of the thread spool. Align the hole in the thread spool with the spool pin positioned at the top of the sewing machine. Press the thread spool onto the spool pin.
Raise the take-up lever to the highest position. The take-up lever is an arm that protrudes on the left side of the sewing machine. To elevate the take-up arm, manually turn the balance wheel (the large wheel on the top of the right side of the machine).
Thread through the thread guide. The thread guide is a notch behind the take-up lever on the back of the left side of the machine. Pull thread from the spool through the thread guide and then down between the tension discs located on the bottom left of the machine below the thread guide.
Thread through the take-up lever. Pull the thread straight up from the tension discs and slide it through the notch on the take-up lever from the back to the front.
Thread the needle. Pull thread down through the thread guide on the front of the face plate and then the thread guide on the needle clamp. Pull the thread to give slack, and thread through the needle from front to back.
Use adequate lighting when threading the machine. Small parts are involved and threading the needle can be cumbersome in dim light.