CHAPTER 2 MEASURING AND REPAIR INSTRUMENTS You, as an Engineman, must he able to identify the basic  measuring  and  repair  instruments  and  the  basic components  of  these  instruments.  This  chapter  will  help you to recognize the how and when to use and maintain basic measuring and repair instruments and engine test equipment. Measuring  instruments  are  used  to  check  tolerances and  specifications  during  inspections  and  repairs  of internal combustion engines and auxiliary equipment. You, as an Engineman, need measuring instruments to determine what parts are worn and need to be repaired or   replaced.   The   following   measuring   and   repair instruments  are  discussed  in  this  chapter:  dial  indicator, dial/vernier  caliper,  micrometer,  snap  gauge,  bore gauge,  strain  gauge,  borescope,  stroboscope,  torque wrench,  multiplier,  adapter,  ridge  reamer,  cylinder  hone, and  dynamometer. SENSITIVE  MEASURING  TOOLS Sensitive  measuring  tools  are  measuring  devices that provide measurement readings to a thousandth of an inch or less. The more common sensitive measuring tools  you  will  use  are  the  dial  indicator,  dial/vernier caliper, micrometer, snap gauge, bore gauge, and strain gauge. DIAL INDICATOR A  dial  indicator  is  used  to  measure  shaft  runout, shaft  thrust,  gear  backlash,  flywheel  face  runout, flywheel   housing   concentricity,   and   valve   seat concentricity. You can mount a dial indicator on a test stand or, with clamps and a magnetic base, directly on the  equipment  to  be  measured.  Figure  2-1  shows  a typical dial indicator with mounting accessories, Most  dial  indicators  have  components  such  as  a bezel, indicator pointer, tool post and clamp, magnetic toolholder,  and  sensor  button  that  are  used  in  taking measurements. The  following  procedures  explain  how  to  use  the indicator to take shaft runout and crankshaft end play measurements.   Procedures   for   taking   other measurements are similar. Figure 2-1.—Typical dial indicator wlth mounting accessories. Shaft Runout When you need to measure a shaft’s runout, select a   suitable   position   on   the   shaft,   free   of   keyways, corrosion,  or  other  damage.  Clean  the  surface  and remove any burrs around scratches or dents. To take the runout measurement, use the following procedure: 1.  Place  the  shaft  in  well-oiled  V-blocks.  If  the shaft is a crankshaft, place the bearing journals in the V-blocks. 2.   Attach the magnetic base to a machined surface. Mount the dial indicator on a tool mounting holder and attach the holder to the base. 3.   Adjust the mounting post so you can easily read the face of the dial. 2-l