TM 10-8400-201-23 3-12.  REPAIR AND MAINTENANCE-Continued CAUTION Do Not Use Substitute Thread.  Do Not Use Iron-On Patches For Repairs. Garments may be patched using stitched patches and non-melting nylon thread, size E, NSN 8310-00-492-8397. (b) Stitching and restitching.  When possible all sewing shall be machine sewn.  Regulate the number of stitches as cited in table 3-1.  The thread tension shall be adjusted so that there will be no loose stitching or excessively tight stitching resulting in puckering of the material sewn.  When ends of machine stitching type 301 are not caught in other seams or stitching, they shall be back-stitched not less than 1 inch.  Ends of a continuous line of stitching shall overlap not less than 1/2 inch (1.27 cm).  Thread breaks shall be repaired by stitching back over the break not less than 1/2 inch (1.27 cm).  Thread tension shall be properly maintained to avoid loose stitching and locks shall be embedded in the center of the  material  sewn.    Thread  breaks  in  overedge  stitching  shall  be  overlocked  not  less  than  3/4  inch  (1.91  cm)  at  each break.    Stitch  spacing  used  on  new  replacement  section,  resitching,  and  types  of  seams  shall  be  the  same  as  in  the original construction.  Seams with loose and/or weak thread shall be restitched.  For illustrations of the various types of stitches  used,  see  FED-STD-751.    The  following  types  of  stitch,  thread  size,  and  stitches  per  inch  are  to  be  used  as applicable to the repair. Table 3-1.  Stitching Instructions STITCH THREAD STITCHES ITEM NO. LOCATION TYPE NEEDLE BOBBIN PER INCH 1 and 2 General 301 E E 10-12 1 and 2 General 401 E E 10-12 1 and 2 Overedge 502 E E 6-10 Stitching 503 504 Safety Stitch 515 E B 10-12 516 519 1 and 2 * Bartacks Bartacks E E 18 per bartack 1 and 2 * Buttonholes Buttonholes E E 44-46 per buttonhole 1 and 2 Buttons 101 or E - 20-24 per 301 E button * May be repaired by hand using double ply of E thread. 3-14