MIL-DTL-44400A
3.3.2 Stitching, machine.
*3.3.2.1 Types. All stitch types, except bartacking, shall conform to ASTM-D-6193 as
follows:
a. For all stitching except zig-zag stitching and stitching indicated by "Z" on
drawings type 301, 5 to 7 stitches per inch.
b. For zig-zag stitching - type 304, 12 to 16 stitches per inch.
c. For stitching indicated by "Z" on drawings fasteners type 401, 5 to 7 stitches
per inch.
d. Bartacking. Bartack length shall be as specified on drawings, 1/8 inch in width
(bight) and shall be free of thread breaks and loose stitching.
3.3.2.2 Thread breaks. Thread breaks in stitching shall be overstitched not less than 1 inch
at each break on stitch type 301, not less than ¾ inch at each break on stitch type 304 and not less
than 1 ½ inches at each break on stitch type 401. Thread breaks in type 401 stitching may be
overstitched with stitch type 301. Thread breaks noted during inspection shall be repaired by
overstitching the existing stitching starting from a distance of 1 inch beyond the break, across the
defective area, to a distance of 1 inch beyond the break. The ends of repair stitching are not
required to be backstitched.
3.3.2.3 Stitching ends. The ends of 301 stitching shall be overstitched not less than 1 inch
except where ends are turned under in a hem or held down by other stitching. Where 301
stitching is performed automatically on stitch patterns such as box, box with cross-stitch, "W"
stitching or straight line tacking, not less than three tying, overlapping , or back stitches shall be
used to secure the ends of stitching. The ends of type 304 stitching shall be firmly secured by
backstitching or overstitching or by increasing the number of stitches per inch at the ends for a
minimum of ¼ inch.
3.3.2.4 Skipped stitches. Two or more consecutively skipped stitches occurring in type
301 or 304 stitching shall be overstitched not less than 1 inch. Any skipped stitches in type 401
stitching shall be overstitched not less than 1 ½ inches. Skipped stitches in 401 stitching may be
overstitched with type 301 stitching. Skipped stitches noted during inspection shall be repaired as
specified for thread breaks (see 3.3.2.2).
3.3.2.5 Thread lubricant. The addition of any lubricant to the polyester sewing thread
prior to or during the sewing operation is prohibited.
3.3.2.6 Automatic stitching. Automatic stitching machines may be used to perform any of
the required stitch patterns provided the requirements for the stitch pattern, stitches per inch and
size and type of thread are met and at least three or more tying, overlapping or back stitches are
used to secure the ends of stitching.
3.3.2.7 Thread ends. All thread ends shall be trimmed to a length of not more than ¼
inch.
3.3.2.8 Stitching margins. Unless otherwise specified, all stitch margins shall be 1/8, +
1/16 0 inch.
3.3.3 Splicing of cloth. There shall be no splicing of roof, wall, liner or floor panels. The
number of panel seams shall not exceed requirements specified on the applicable drawings.
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