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Use of the Hand-sewn Hidden Stitch and the Needle Used | Up
Aircrew Survival Equipmentman 2 - Aviation theories and other practices | Next
Uses of Varying Classes of Machine-sewn Seams and Stitchings |
Figure 10-31.—Hidden stitch.
239.380
In this section, we discuss techniques concerning
machine-sewn seams. While there is generally no
option in choosing a hand-sewn seam, there are
many options in choosing a machine seam.
Advantages and Characteristics
of a Machine-Sewn Seam
Machine seams or stitchings have the
following advantages over hand-sewn seams: (1)
speed, (2) appearance, and (3) uniformity of
tension. Their desirable characteristics are as
follows:
STRENGTH. Strength of a seam of stitching
depends on the type of thread, stitch type, number
of stitches per inch, the construction and tightness
of the seam, and the size and type of needle point
used. The strength of the seam should equal that
of the material it joins. Use only the material
specified for the assembly in the applicable
technical order.
ELASTICITY AND FLEXIBILITY. Elas-
ticity and flexibility depend on the stretching
qualities of the material used, the quality and
tension of the thread, the length of the stitch, and
type of seam or stitch used.
DURABILITY. Durability is determined by
the wearing qualities of the material, the quality
of the thread used, and proper tension to set
stitches well into the material to reduce abrasions.
Relationship between the elasticity of the seam
and the elasticity of the material is very important
in determining durability.
SECURITY. The security of a seam or
stitching depends chiefly on the stitch type and
its ability to resist unraveling. The stitch must be
well set in the material to prevent snagging, which
can cause thread breakage and unravel some types
of stitches. Seam “run offs” weaken a seam. All
seam ends should be backstitched or anchored
(backstitched and overstitched) to prevent the
seams from unraveling, as illustrated in figure
10-32.
APPEARANCE. The appearance of a seam
is controlled by its construction and neatness of
workmanship; however, appearance is of less
importance than any of the four factors explained
previously—strength, elasticity, durability, and
security. Size and type of thread and length of
stitch may also affect appearance.
Meanings and Symbols of
Machine-Sewn Basic Stitches
Meanings and symbols of basic machine-sewn
stitches are discussed in the following paragraphs.
Figure 10-32.—Properly anchored machine seam.
10-25
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