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Use of the Hand-sewn Hidden Stitch and the Needle Used
Uses of Varying Classes of Machine-sewn Seams and Stitchings

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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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