CHAPTER 2 MEASURINGTOOLSANDTECHNIQUES When performing  maintenance  and repair  tasks  on catapults  and  arresting  gear equipment, you must  take accurate measurements during   inspection, to  determine the   amount     of  wear   or  service   life   remaining on  a particular    item  or to make sure replacement parts  used to  repair  equipment meet established specifications. The accuracy  of  these  measurements,  often  affecting   the performance and    failure rates    of  the    concerned equipment,  depends on the  measuring tool you  use and your   ability    to  use it   correctly. Upon completing this   chapter you should be able to do the  following: l Select  and   use  rules,   tapes,  and   inside   and outside   calipers. l Transfer    measurements    from   one  caliper    to another. l Maintain and  inventory     precision   measuring equipment    used  to  perform   maintenance    on catapults  and  arresting  gear. Use and  Care of Hand   Tools and  Measuring  Tools, NAVEDTRA     12085, is   an   excellent   reference  to  use while  you  are  studying  this   chapter. COMMON MEASURING TOOLS You  will    use  many   different    types  of measuring tools  in   the   daily    performance  of  your   duties.  Where exact  measurements   are  required,    use  a  micrometer caliper (mike).    If   you   use  the   micrometer caliper properly, it   will     allow    you   to  measure    within one ten-thousandth (0.0001 )  of an  inch   accuracy.  On  the other  hand,  where  accuracy is  not  extremely  critical,   a common straightedge   rule   or  tape  rule  will   suffice  for most  measurements. RULES   AND   TAPES Figure   2-l   illustrates     some of the  commonly  used straightedge  and  tape rules.  Of all  measuring tools, the simplest    and   most   common   is  the   steel   or  wooden straightedge    rule.   This   rule   is  usually    6 or  12 inches long,  although   other   lengths   are  available.  Steel  rules may be flexible  or nonflexible,  but  the  thinner   the  rule is, the easier it  is  to measure accurately with  it,  because the    division marks     are   closer   to   the   work    to   be measured. Generally, a rule  has four  sets of graduated division marks,  one on each edge of each side of the  rule.  The longest  lines   represent  the  inch   marks.  On  one edge, each inch  is  divided  into  8  equal spaces, so each space represents    l/8   inch.   The   other   edge  of  this    side  is divided    into    sixteenths.     The    l/$-inch and    l/2-inch marks   are  commonly  made  longer   than   the   smaller division  marks to facilitate  counting, but  the graduations are  not  normally    numbered  individually, as they   are sufficiently   far   apart   to  be counted without    difficulty. The  opposite side of the  rule   is  similarly    divided   into 32 and 64 spaces per inch,  and it  is common practice to number  every  fourth   division  for  easier reading. There   are  many   variations    of  the   common rule. Sometimes    the   graduations are  on  one  side  only, sometimes a set of graduations  is added across one end for measuring in  narrow spaces, and sometimes only  the first    inch   is  divided    into   64ths,  with    the   remaining inches divided  into  32nds and  16ths. Steel tapes  are  made from  6 to  about  300 feet  in length.  The shorter  lengths  are frequently  made with   a curved cross section so that  they  are flexible  enough to roll   up,  but   remain   rigid    when   extended.   Long,  flat tapes   require    support    over   their     full    length    when measuring,   or  the  natural    sag will    cause an  error   in reading. a3Nvso71 rLm STEEL   RULE a’ r HOOK  RULE FOLDING RULE Figure    Z-l.-Some common   types    of   rules. 2-1