TM   9-2815-202-34 c.   Repair (1) General. Procedures for repair will be the same for a great percentage of parts and components.  To  avoid  repetition  of  instructions,  general  procedures  for  repair  are  detailed  in paragraphs  below.  After  repair,  clean  all  parts  thoroughly  to  prevent  metal  chips  from  repair operations,  or  abrasives  used  in  repair  operations  from  entering  working  parts  of  the  engine. CAUTION Avoid  damage  to  casting  while  using welding   instructions. (2) Castings. welding  equipment.  Refer  to  TM  9-237  for (a) (b) (c) (d) (e) (9) Replace all castings that are cracked or do not conform to tolerances specified in App G. Repair minor damage to machined surfaces with a fine file, emery cloth, or crocus cloth dipped in cleaning solvent. Replace all castings on which machined surfaces are burred or nicked to the point of impairing  subsequent  assembly  or  operation. Repair  minor  warpage  of  mounting  flanges  and  gasket  surfaces  by  working  surfaces across a sheet of emery cloth held tightly on a surface plate or a flat surface. Finish similarly  using  crocus  cloth. Replace  castings  having  flanges  which  are  warped  to  the  point  of  impairing  assembly  or operation. Repair damaged pipe or cap screw threads in tapped holes with a thread tap. Pipe-plug  threads (3) Ball Bearings. in castings must be NOTE in good condition to prevent oil or water leakage. (a) (b) Replace all galled, pitted, or damaged ball bearings and any that do not conform to tolerances  specified  in  App  G. See TM 9-214  for  maintenance  of  bearings. (4)  Studs. (a) Replace all bent or loose studs or studs showing evidence of stretching. (b) Repair minor thread damage with a thread chaser. 3-5