WARNING WARNING TM  6-6675-302-14&P Section III. REPAIR OF TRIBRACH ASSEMBLY 5-5.  General.  The  tribrach  assembly  consists  of the  base  plate,  leveling  screws,  circular  level,  op- tical  plumbing  device,  and  tribrach,  which  form  a leveling base between the target set and the tripod head. The base plates provide a means for securing the theodolite to the tripod, with the utilization of the  tripod  bridge  screw.  Leveling  is  accomplished by  means  of  the  leveling  screws.  Precise  location of  the  target  set  over  the  station  point  is  verified by sighting through the optical plumbing eyepiece. 5-6. Base Plate. a. Removal. (1) Remove  the  tribrach  assembly  (para.  4-9). (2)  Refer  to  figure  5-1  for  model  242406.  On model USATS-79 the base plate is removed during disassembly. b.  Disassembly.  Refer  to  figure  5-2  for  model 242406, or figure 5-3 for model USATS-79. c. Cleaning, lnspection  and Repair. Clean parts in a well-ventilated area. Avoid inhalation of solvent fumes and prolonged exposure of skin to cleaning solvent. Wash exposed skin thoroughly. Dry   cleaning   solvent   (Fed.   Spec. P.D-680) used to clean parts is potential- ly dangerous to personnel and property. Do not use near open flame or excessive heat. Flash point of solvent is 100F to 138F (38C to 59C). (1) Clean all parts using cleaning solvent and dry  thoroughly. (2) Inspect the base plate and the spring plate for  dents,  cracks,  breaks,  and  burrs.  Inspect  all threaded parts and hardware for worn or damaged threads. (3) Remove all burrs and minor dents. (4) Replace  all  defective  parts  that  cannot  be repaired. d.  Reassembly.   Refer  to  figure  5-2  for  model 242406  or  figure  5-3  for  model  USATS-79,  and reassemble the base plate. e.  Installation.   Refer  to  figure  5-1  for  model 242406,  and  install  the  base  plate.  On  model USATS-79,   the   base   plate   is   installed   during reassemby. 5-2 5-7. Leveling Screws (Model 242406), and Foot Screws (Model USATS-79). a. Removal and Disassembly. (1) Remove the base plate (para 5-6). (2) Refer  to  figure  5-4  on  model  242406,  remove and  disassemble  the  leveling  screws.  On  model USATS-79  refer  to  figure  5-5  and  remove  the footscrew  assembly. b. Cleaning, Inspection and Repair. Clean parts in a well-ventilated area. Avoid inhalation of solvent fumes and prolonged exposure of skin to cleaning solvent. Wash exposed skin thoroughly. Dry   cleaning   solvent   (Fed.   Spec. P-D-680) used to clean parts is potential- ly dangerous to personnel and property. Do not use near open flame or excessive heat. Flash point of solvent is 100F to 138F (38C to 59 C). (1) Clean all parts using cleaning solvent and dry  thoroughly. (2) Inspect  the  spindles  for  bends.  Inspect  all threaded parts for worn or damaged threads. (3) Replace  all  defective  parts  that  cannot  be repaired. c. Reassembly and Installation. (1) Refer  to  figure  5-4  on  model  242406  then reassemble   and   install   the   leveling   screws.   On model USATS-79 refer to figure 5-5 then reassem- ble and install the footscrew assembly. (2) Install the base plate (para 5-6). d. Adjustment.  Loosen the adjusting screw and turn leveling screw (model 242406), figure 5-4. On model USATS-79 refer to figure 5-5 and tighten the adjusting screw. 5-8. Circular Level. a. Removal and Disassembly. (1) Remove the base plate (para 5-6). (2) On  model  242406  refer  to  figure  5-6,  remove and disassemble the circular level. (3) On  model  USATS-79 and remove the circular level. refer  to  figure  5-10