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
