TM 1-1520-240-BD SECTION II.  GENERAL STRUCTURAL REPAIRS 2-4.   RIVETS.    Refer  to  TM  1-1500-204-23  Series  for riveting     procedures     and     identification.          Additional information   on   rivets,   including   alloy   selection,   row distance, and pitch, as may be necessary to accomplish repairs is shown.  Acceptable rivet inspection criteria is as follows: a. The  head  of  a  flush  rivet  should  be  flush  with the surface with no significant deviation above or below this    level.        The    rivet    should    be    centered    in    the countersink  to  provide  continuous  contact  around  the head of the rivet. b. The   head   of   a   protruding   head   rivet   should provide   continuous   contact   with   the   surface;   that   is, there  should  be  no  significant  head  tit  relative  to  the surface. c. The   tails   of   both   of   the   above   rivets   should provide  continuous  circumferential  contact  between  the tail and the local surface. d. There should be no damage to the rivet or local surface such as that resulting from bucking bar slippage. e. A truly loose rivet will be moveable by hand and should be replaced. 2-5.  SUBSTITUTE AN BOLTS FOR AN RIVETS . Substitute AN bolts for AN rivets as follows: a. When   rivets   left   out   on   assembly   cannot   be installed. b. Where  edge  distance  is  less  than  1  1/2  times diameter of rivet. NOTE Minimum edge distance of two times diameter of rivet is preferred. c. Replacement sizes are as follows: RIVET ALLOY AND DIA BOLT SIZE AD4, 5, 6 AN3 or AN23 AD8 AN4DD or AN24 AD10 AN5DD or AN25 AD12 AN6DD or AN26 2-6.       INSTALLATION    OF    AN    BOLTS    FOR    AN RIVETS. a. Drill rivet hole to size as follows: RIVET ALLOY HOLE DIA AND DIA BOLT SIZE (INCHES) AD4, 5, 6 AN3 or AN23 0.191 to 0.197 AD8 AN4DD or AN24 0.250 to 0.257 AD10 AN5DD or AN25 0.3125 to 0.3195 AD12 AN6DD or AN26 0.375 to 0.382 b. Install   washers   AN960   and   nuts   MS20364   as required. c. Nuts MS20365 can replace nuts MS20364. 2-37