RIVET REPLACEMENT - Contd
After drilling but before driving rivets, the parts must be held securely in position to prevent slippage during
riveting. When two pieces of metal have been drilled through, use any of several types of available skin
fasteners to hold them in alignment.
MACHINE STITCHING. All stitch types, except bartacking, shall conform to FED-STD 751. Type 301 and 401
stitching requires 5-7 stitches per inch. Bartacking shall be 1/8 inch in width and free of thread breaks and loose stitching.
Thread Breaks. Thread breaks in stitching shall be overstitched not less than 1 inch at each break on stitch
type 301, and not less than 1 1/2" at each break on stitch type 401. Thread breaks in type 401 may be overstitched with
stitch type 301. Thread breaks noted during inspection must be repaired by overstitching the existing stitching starting
from a distance of 1 inch beyond the break. The ends of repair stitching are not required to be backstitched.
Stitching Ends. The ends of type 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 performed automatically on stitch patterns
such as box, box with cross-stitch , "W" stitching or straight line tacking, at least three tying, overlapping, or back stitches
shall be used to secure the ends of stitching.
Skipped Stitches. Two or more consecutively skipped stitches occurring in type 301 stitching shall be
overstitched not less than 1 inch. Any skipped stitches in type 401 stitching shall be overstitched not less than 1 1/2
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 in a., above.
AUTOMATIC STITCHING. Automatic stitching machines may be used to perform any of the required stitch
patterns provided the requirements of the stitch pattern, stitches per inch, size and type of thread are met, and at least
three or more overlapping, tying or backstitches secure the ends of the stitching.
SETTING OF GROMMETS. Holes punched to receive grommets shall be smaller than the outside diameter of
the grommet barrel so that the barrel must be forced through the hole. The grommets shall be securely clinched without
cutting the materials.