TM 5-3825-226-24 CONNECTING RODS Leave the connecting rod in the checking fixture and check  for  both  bores  parallel.    Make  a  record  of  the readings  for  both  dial  indicators.    The  total  difference between     indicator     readings     is     the     bores     parallel dimension.  The maximum allowable dimension is .006 in. for rods that are acceptable for reconditioning. A  check  can  also  be  made  to  check  for  connecting rod twist.  Push one end of the pin mandrel against the locating surface behind it.  Use a thickness gauge on the opposite    end    to    check    the    clearance    between    the mandrel  and  the  locating  surface.    Check  both  ends  of the  mandrel  in  this  way  for  clearance.    The  amount  of clearance   is   the   twist   in   the   rod.      The   maximum allowable twist is .012 in.  for rods, that are acceptable for reconditioning. BORING PISTON PIN BEARING After  new  piston  pin  bearings  are:    installed  in  the connecting    rods,    use    the    5P3550    Connecting    Rod Boring  Machine  to  bore  the  piston  pin  bearings  to  the correct size. Install  the  cap  on  the  connecting  rod  (do  not  install the   bearings).      Tighten   the   nuts   as   shown   in   the SPECIFICATIONS. Put-the  5P2010  Mandrel  on  the  spindle.    Install  nut and  actuator,  and  tighten  to  hold  mandrel  in  position. Install  5P2013  Plunger  Extension  on  the  plunger.    The plunger must be in the up position within ±  3°.  Loosen the spindle carrier, and use the handle on top to adjust the bearing bore center-to-center dimension.  Move the carrier  until  the  vernier  scale  reads  7.6867  ±  .0010  in. This is the correct scale dimension to get a bearing bore center-to-center    dimension    of    7.9000    ± .0010    in. Tighten the carrier in this position. Put  the  connecting  rod  in  position  on  the  mandrel, with the boss on the pin end of the rod towards the left. Turn the actuator until the connecting rod is tight on the mandrel. Install 5P3552 Bushing in the front bracket.  Push the locating  arbor  through  the  front  bushing.    Put  5P3541 Locating   Bushing,   with   the   large   dimension   of   the diamond shape horizontal, on the locating arbor.  Slide the  locating  arbor  through  the  connecting  rod  and  into the rear bushing.  Slide the locating bushing into the rod. Push    the    locating    rods    until    they    are    against    the connecting rod, and tighten the rods firmly.  Remove the locating arbor end bushing. Fasten  the  5P2023  Tool  Bit  Setting  Gauge  to  the boring bar.  Be sure the contact point of the indicator is against   the   boring   bar.      Adjust   the   indicator   so   the revolution counter and the hand are at zero.  Move the tool bit setting gauge so that the contact point is against the cutting edge of the tool bit.  Fasten the gauge in this position.  Loosen the screw that holds the tool bit.  Make an  adjustment  to  the  tool  bit  until  the  indicator  reads .1881  in.    Tighten  the  screw  that  holds  the  tool  bit  and recheck the setting. Put  the  boring  bar  through  the  connecting  rod  and into the rear bushing.  Install the front bushing over the boring bar and into the bracket.  Install 5P4777 Torsion Bracket on the rear of the boring machine.  Put 5P4778 Feed   Cylinder   so   the   shaft   goes   through   the   rear bushing and into the boring bar.  Tighten the setscrew in the  boring  bar  to  hold  the  feed  cylinder  shaft.    Adjust torsion   bracket   and   feed   cylinder   so   the   boring   bar moves smoothly in rear bushing. NOTE:    Put  the  feed  lever  on  the  feed  cylinder  in  the OPEN position before moving the boring bar. With the feed lever in the OPEN position, move the boring bar until the tool bit is .125 in.  (3.2 mm) from the bearing in the connecting rod.  Put the feed lever in the CLOSED  position  and  tighten  the  thumbscrew  on  the cylinder    against    the    torsion    bracket    shaft.        Install 5P2055  Flexible  Adapter  in  the  front  of  the  boring  bar and fasten an electric drill to the adapter.  Put oil on the boring bar at the front and rear bushings.  Start the drill and let the feed cylinder pull the boring bar through the bearing.    Use  a  slow  feed  rate  and  do  not  push  on  the drill. Check the bearing bore with a new piston pin.  If the fit  is  too  tight,  do  the  boring  operation  again  with  the SAME tool bit setting. Install the connecting rod into the piston with the boss on the rod on the same side as the crater in the piston. CONNECTING ROD AND PISTON When    the    connecting    rod    and    piston    assembly    is installed, use new connecting rod bolt nuts. 3-382