OSCILLATING TYPE SEWING MACHINES

239.262 Figure 9-2.—Sewing machine 31-15. The machine is powered by an electric motor, which is connected to the motor driving pulley by a clutch. You connect the motor to the clutch by pressing the forward part of the foot treadle. The aft part of the treadle is the brake, which acts upon the clutch. The material to be sewn is held in position on the feed dog by the presser foot. The pressure of the presser foot upon the material enables the feed dog to push the material forward each time the needle goes up. The pressure of the presser foot on the material is released either by a knee lifter or a hand lifter. The presser foot can be raised by pushing the knee lifter to the right. The hand lifter is located behind the face of the machine. The presser foot may be lifted and locked into position by raising the hand lifter to its highest position. OSCILLATING TYPE SEWING MACHINES Two of the most commonly used oscillating sewing machines are the 31-15 and 7-33, both of which are discussed in this chapter. SINGER SEWING MACHINE 31-15 When starting out as a PR, the 31-15 sewing machine will probably be the one you’ll like to use. This machine is smaller and lighter than most of the other machines used in the parachute loft. The manufacturer calls the 31-15 a tailoring machine. It is used to sew and repair clothing, uniforms, shirts, flying clothing, jackets, and lightweight protective covers. The 31-15 is an oscillating sewing machine that has a recommended speed of 2,200 stitches per minute and makes a lockstitch. It is very good for sewing nylon cloth, and can be used for sewing lightweight canvas up to 8 ounces. The number of stitches can be regulated from 7 to 32 stitches per inch. When the 31-15 machine is in operation, the balance wheel turns over toward the operator. When hand-turning the balance wheel, always rotate it in this direction. The components of the Singer Sewing Machine 31-15 are shown in figure 9-2. 9-3