TM 9--2815--247--34 0012 00--6 GENERAL MAINTENANCE INSTRUCTIONS -- CONTINUED 0012 00 GENERAL REPAIR General Most engine parts and components may be repaired as outlined below. After repair, clean all parts thoroughly to prevent metal chips from repair operations, or abrasive used in repair operations, from entering working parts of engine. General Repair of Castings Replace all castings when cracks have penetrated high stress areas such as fillets or webbing. Replace all castings which do not conform to tolerances specified in the appropriate repair standards table. WARNING Replace all castings on which machined surfaces are burred or nicked to the point of impairing subsequent assem- bly or operation. Repair minor damage to machined surfaces with a fine mill file or crocus cloth dipped in dry-- cleaning solvent (item 5, WP 0100 00). Replace all castings having flanges which are severely warped and cannot be repaired to provide a proper seating surface with its mating part. Repair minor warpage of mounting flanges and mounting pads by working surface across a sheet of crocus cloth held tightly on a surface plate or similar flat surface. CAUTION Pipe plug threads in castings must be in good condition to prevent oil leakage. Repair damaged pipe threads in tapped holes with a used tap. Ball and Needle Bearings Replace all galled, pitted, or damaged bearings. Replace all bearings which do not conform to tolerances specified in the appropriate repair standards table. Refer to TM 9--214 for information on inspection, care and maintenance of anti--friction bearings. Studs Replace all bent or loose studs or studs showing evidence of stretching. Repair minor damage with a thread chas- er. Replace all studs having stripped or damaged threads. Remove and replace studs as outlined below. Stud identification  Stud identification tables appear in the repair sections of Chapters 3 and 4. Each table con- tains the appropriate information regarding stud setting heights, number required and reference figures of stud identification and location. Removal  Using a stud extractor, back studs out slowly to avoid heating and possible seizure. When studs are broken off too short to use extractor, drill stud and extract with a suitable remover. Short studs may also be re- moved by welding a piece of bar stock or a nut to stud and removing with a wrench.