TM 5-3805-260-24 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   allow-able   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.   In, tall 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 resolution 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 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 slows 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. 3-384