TM 10-3930-669-20 d. Screws, Nuts, and Fittings.  Replace any screw, nut, or fitting with damaged threads.  Inspect tapped holes for thread damage.  If cross-threading is evident, retap the hole for the next oversize screw or stud.  If the retapping will weaken the part, or if the cost of the part makes retapping impractical, replace the part.  Chasing the threads with proper size tap or die may be adequate. e. Stud  Installation.    When  installing  studs,  use  a  proper  driver.    A  worn  stud  driver  may  damage  the  end thread and a chasing die must be used before a nut can be installed.  This procedure will remove cadmium plating and allow  corrosion.    Before  installing  a  stud,  inspect  the  hole  for  chips.    Blow  out  foreign  matter  and  start  stud  by  hand. Before installation, coat thread with a film of antiseize compound.  Install stud to proper "setting height," which is the total projecting length. f. Dents.    Straighten  minor  body  dents  by  bumping  with  a  soft-faced  hammer  while  using  a  wooden  block backing. 2-26.  GENERAL ASSEMBLY INSTRUCTIONS . a. Preparation. Remove protective grease coatings from new parts before installation. b. Performed  Packing  Installation.      Clean   groove   that   performed   packing   is   to   be   installed   in   before installation.  Lubricate performed packing, prior to installation, with a clean lubricant.  This lubricant must be of the same type used in the component the performed packing is to be installed in.  Do not over-stretch performed packing during installation.  Use care not to cut performed packing during installation. c. Pipe Joints and Fittings.  Use non-hardening sealing compound or Teflon pipe sealant to join piping and fittings. d. Oil Seals.    Coat  oil  seals,  before  installing,  with  clean  lubricant.    This  lubricant  must  be  of  the  same  type used  in  the  component  the  oil  seal  is  to  be  installed  in.    Wipe  all  excess  lubricant  from  side  of  oil  seal  that  is  on  the outside of the component (away from lubricant).  Install oil seals with seal lip facing toward lubricant, applying an even force to the outer edge of the seal.  If oil seals are to be installed over keyed or splined shafts, use a guide to prevent sharp edge of keyway or splines from cutting the seal.  Construct guides of very thin gauge sheet metal and shape to the required diameter.  Make certain guide edges are not sharp and are bent slightly inward so they do not cut the seal. e. Bearings  and  Shafts.    When  mounting  bearings  on  shafts,  always  apply  force  to  the  inner  races.    When mounting bearings into housing, always apply the force to the outer race. f. Bearing Lubrication.  Lubricate bearings, before assembly, with clean lubricant.  This lubricant must be of the same type used in the component the bearing is to be installed in. 2-493