TM 1-1520-240-BD 2-10.  REPLACE     OR     SUBSTITUTE     BOLTS     FOR SCREWS. a. AN    standard    hex    head    or    clevis    bolts    can replace or substitute screws AN525. b. No AN standard hex head or clevis bolts can be replaced or substituted by screws. c. Aluminum    alloy    bolts    must    not    replace    or substitute steel screws. 2-11.  BOLT HOLE STANDARDS. a. Before    replacing    fitting    installed    with    bolts, check holes in fitting and structure for oversize or oval. b. Bolts    0.0625-inches    larger    in    diameter    than original  bolts  can  be  used.    Only  one  oversize  bolt  is allowed for each fitting. c. Edge distance and hole sizes must be as follows on Table 2-2. 2-12.  USE OF NUTS.  WASHERS, OR COTTER PIN . a. Use nut and bolt as follows: (1) Both nut and bolt are same material. (2) When  damaged,  replace  with  same  size, material, and hardness as original nut or bolt b Use  aluminum  alloy  washers  under  aluminum alloy nuts and bolts. c. Use aluminum alloy washers under steel nut on bolt  heads,  attaching  aluminum  parts  when  not  under tension forces, or a controlled torque is not required. d. Use  cadmium  plated  steel  washers  under  steel nuts or bolt heads attaching steel parts. e. Use  cadmium  plated  steel  washers  under  steel nuts or bolt heads, attaching aluminum alloy parts when bolt  is  under  tension  forces,  or  a  controlled  torque  is required. f. Steel   spring   washers   may   be   used   a   second time if replacements are not available. g. Cotter pin must not be used a second time. SECTION III.  MAINTENANCE AND REPAIR PROCEDURES 2-13.  ADHESIVE BONDING. a. General. Subsequent paragraphs contain procedures  for  the  mixing  and  application  of  bonding agents.  These  procedures  should  be  used  only  when referenced in this manual.  For non-critical applications the procedures may be used without specific reference. To   obtain   optimum   benefit   from   the   information   and tables, select the proper adhesive as follows: (1) Determine  the  type  of  the  material  to  be bonded.    Cross  reference  trade  names  to  the  type  of material. (2) Determine the appropriate adhesive systems   by   matching   materials   in   Table   2-3.      An adhesive  system  may  include  more  than  one  type  of adhesive,  since  several  adhesives  may  be  identical  in physical properties and use. (3) Determine which adhesive system is most suitable.  Table 2-4 lists the criteria for each system. (4) Select  the  adhesive.    Table  2-5  lists  the adhesive     system     numbers     and     the     corresponding acceptable adhesives.  Refer to the task number given in    the    column    APPLICATION    AND    CURE    for    the acceptable method of bonding. b. Criteria   for   Application   of   Adhesive   Systems. This information is applicable to all adhesives and must be strictly adhered to. (1) If  the  adhesive  or  individual  components of  adhesive  have  been  stored  under  refrigeration  allow adhesive or components to reach 70°  F (21.1 °C), prior to blending or use. 2-45