caused personnel injury, damage to equip- ment,   and   unnecessary   interruption   of propulsion   power. 1.  Cut  the  tubing  square  and  lightly  deburr the  inside  and  outside  corners.  For  corrosion resisting  steel  (CRES)  tubing,  use  a  hacksaw  rather than a tubing cutter to avoid work hardening the tube  end.  For  CRES,  and  if  necessary  for  other materials, dress the tube end smooth and square with a file. Tube ends with irregular cutting marks will  not  produce  satisfactory  seating  surface impressions. 2. Test the hardness of the ferrule by making a light scratch on the tubing at least 1/2 inch back from  the  tube  end,  using  a  sharp  corner  on  the ferrule.  If  the  ferrule  will  not  scratch  the  tube, no bite will be obtained. This test maybe omitted for  flush-type  ferrules  where  the  bite  will  be visible. Moderate hand pressure is sufficient for producing  the  scratch. 3.  Lubricate  the  nut  threads,  the  ferrule leading  and  trailing  edges,  and  the  preset  tool threads with a thread lubricant compatible with the system. Slide the nut onto the tubing so the threads  face  the  tube  end.  Note  whether  the ferrule is a flush type or recessed type (fig. 5-19), and slide the ferrule onto the tube so the cutting edge  is  toward  the  tube  end  (large  end  toward  the nut). 4.  Bottom  the  end  of  the  tubing  in  the presetting  tool.  Slide  the  ferrule  up  into  the presetting tool, and confirm that the nut can be moved  down  the  tube  sufficiently  to  expose  at least 1/8 inch of tubing past the ferrule after the presetting  operation  (fig.  5-20)  to  allow  for inspection  of  the  ferrule. 5.  While  keeping  the  tube  bottomed  in  the presetting  tool,  tighten  the  nut  onto  the  fitting body  until  the  ferrule  just  grips  the  tube  by friction. This ring grip point may be identified by lightly  turning  the  tube  or  the  presetting  tool  and slowly  tightening  the  nut  until  the  tube  cannot be  turned  in  the  presetting  tool  by  hand. Mark  the  nut  and  the  presetting  tool  at  this position. 6.  Tighten  the  nut  according  to  the  number of  turns  given  in  table  5-3,  depending  on  tube size. 5-16 Figure  5-20.—Tube  and  ferrule  assembled  for  preset- ting, showing nut position required for inspecting ferrule. Inspection Disassemble and inspect the fitting as follows (mandatory): 1. Ensure that the end of the tubing has an impression  of  the  presetting  tool  seat  surface (circular appearing ring) for 360 degrees. A partial circle, a visibly off-center circle, or a circle broken by the roughness of the tube end is unsatisfactory. 2.  Check  for  proper  bite: a.  For  flush-type  ferrules,  a  raised  ridge (fig. 5-21) of tube metal must be visible completely around the tube at the leading edge of the ferrule. The  best  practice  is  to  obtain  a  ridge  about  50 percent  of  the  ferrule  edge  thickness. Table  5-3.—Number  of  Turns