TM 10-3930-669-34 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. g. Sheet Metal Repair.  Repair minor skin cracks by installing patches. 2-20.  GENERAL ASSEMBLY INSTRUCTIONS. a. Preparation.  Remove protective grease coatings from new parts before installation. b. Preformed  Packing  Installation.    Clean  groove  that  preformed  packing  is  to  be  installed  in  before  installation. Lubricate preformed packing, prior to installation, with a clean lubricant.  This lubricant must be of the same type used in the component the preformed packing is to be installed in.  Do not over-stretch preformed packing during installation.  Use care not to cut preformed 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 with clean lubricant before installing.  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. 2-93