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Zigzag
medium
duty
Harness
machine
heavy
duty
Harness
machine
extra
heavy
duty
Bar tack
Model
Figure 6-63. Sewing machine model comparison.
6-14
Figure 6-62. Pfaff 3334.
6-15
4
3
5
2
1
6
9
7
8
Figure 6-64. Front view of a modern light-duty single needle machine.
1. Machine head—This is the actual machine assembly.
2. Table top—This holds the head in position and the
motor underneath.
3. Stand—This supports the table top.
4. Motor—This powers the sewing machine.
5. Treadle—This is the “gas pedal” which operates the
motor. Pushing forward makes motor start and pushing
backward stops the motor.
6. On/off switch—Controls power to the motor.
7. Thread stand—This holds the spools of thread for
both the sewing machine and the bobbin winder.
8. Bobbin winder—This feeds the thread to the bobbin
during the winding process.
9. Light—A good light is necessary to observe the
sewing operation.
6-16
Figure 6-65 shows a closeup of the head only. Only those
parts, which the rigger must deal with on a regular basis
in order to operate and maintain the machine, are shown.
For those individuals who wish to become more involved
in the machine, a thorough study of the operator’s manual
and parts manual is encouraged. The following numbers
correspond with the part description.
1. Bed—The base of the machine.
2. Arm—The upper casing of the machine.
3. Uprise—The upright part of the machine that joins
the base and the arm.
4. Faceplate—The cover that protects the needle bar
and presser bar mechanisms.
5. Balance wheel—The pulley assembly that drives the
machine via the motor and belt.
6. Reverse lever—The mechanism that, when
depressed, reverses the sewing operation of the
machine.
7. Stitch regulator—The adjustor that controls the
length of the stitch. The larger the number, the longer
the stitch, and the smaller the number, the shorter the
stitch.
8. Pre-tension thread guide—The assembly that provides
initial thread tension and thread straightening
before the thread reaches the main upper thread tension
assembly.
9. Thread retainer—Provides direct guidance for the
thread to the upper tension assembly.
10. Thread take-up cover—Covers the thread take-up
lever and protects the operator.
11. Right arm thread guide—Provides thread guidance
from the upper tension assembly to the thread takeup
lever.
12. Upper tension regulating thumbscrew—Regulates
pressure of the tension discs on the thread.
13. Thread controller spring—Provides for the correct
amount of slack in the needle thread when the needle
1
4
3
5
2
6
12
11
10 8 7
22
21
20
19
18 17
16
15
14
13
9
Figure 6-65. Closeup of head.
6-17
is descending so that the needle does not cut the
thread.
14. Tension discs—Provide tension on the upper thread.
15. Presser bar tension nut—Regulates the pressure of
the presser foot on the material.
16. Thread take-up lever—Provides for slack in the
needle thread after the stitch is formed and pulls the
correct amount of thread from the spool for the next
stitch.
17. Needle bar—Holds the needle and carries the upper
thread downward through the material to where the
stitch is formed.
18. Presser foot bar—Holds the presser foot in place to
hold pressure on the material.
19. Presser foot—Holds the material in place while the
feed dog moves the material forward for the next
stitch.
20. Needle plate—Surrounds the feed dog and protects
the material during the movement process.
21. Slide plate—Covers the area of the bed to the left of
the feed dog and provides access to the bobbin
assembly.
22. Feed dog—Feeds the material through the machine
from the underside.
SEWING THEORY
Once the rigger has become familiar with the parts of the
machines, it is time to begin to understand the operation
and theory of how the machines sew. The primary form of
stitch pattern is what is called a 301 lockstitch. It is
formed by two threads, one from the top and one from the
bottom. The needle carries the thread from the top
through the material, and the bobbin holds the thread on
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Parachute Rigger Handbook(63)
