The Singer 15-91 has a potted motor, a class 15 oscillating bobbin system, and is a straight stitch only sewing machine, but there are blind hemmers, zigzaggers, and a buttonholer, which all can take this straight stitch machine, and turn it into a multi purpose sewing machine, just like the other low shank straight stitch sewing machines.
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| The biggest difference between the 15-91 and other Singer class 15 sewing machines, is the potted motor, on the rear of the machine, near the handwheel. Steel gears drive the machine directly off this motor, so no belt is needed. |
Singer made a variety of class 15 sewing machines, and at the request of the U.S. government, after World War 2, did not file the patent on their class 15 oscillating bobbin sewing machine that could have the separate motor added to the back, so the plans could be used by factories in Japan, to rebuild the manufacturing centers of Japan, after the bombings that ended the war, decimated these areas manufacturing, thereby decimating the economy, as well.
This is why you will find class 15 sewing machines the most common sewing machine in the world, but this specific 15-91, has a different type of motor on it, called the potted motor. The potted motor is attached back by the handwheel, and steel gears drive the machine, without a need for a belt between the motor and the handwheel.
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| Singer 15-91 bobbin area and faceplate with the tension unit. This machine takes regular low shank straight stitch presser feet. |
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| Singer 15-91 with set of accessories, box, and manual (The small screwdriver is missing) |
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| 15-91 tension unit and bobbin area |
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| Notice that Singer included advertising for their various Singer Fashion Aids, and extra attachments, in their manuals, a great way of getting the advertising in front of the right audience! My 15-91 manual has the advertisement for the Universal Threader and seam Ripper, in the back, as well as the "Third Hand" The Singer Material Gripper! |
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| Notice that the difference between the 66-16 and 66-18 is literally the decor! The 15-91 is at the top left, while the 201-2 in in the upper right corner of this advertising flyer.
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