T.O.  1-1A-9 Figure 8-6.  Shore Scleroscope b. A  vertical  glass  tube,  mounted  to  the  base  and containing the cylindrical diamond point hammer. c. A suction heat and bulb for lifting and releasing the hammer. d. A   scale,   visible   through   the   glass   tube,   for determining the height of the rebound. e. A  magnifier  hammer  with  a  larger  contact  area is supplied for use with extremely soft metals. 8-20.  TESTING WITH THE SCLEROSCOPE.  The test is made as follows: 1. Level the instrument by means of the adjusting screws   (1).      (See   figure   8-6).      The   level   position   is determined by means of the plumb rod (2). 2. Prepare  the  test  specimen  as  described  for  the Brinell and Rockwell tests in preceding paragraphs and clamp it on the base.  This is done by raising the lever (3)  inserting  the  sample  and  exerting  the  pressure  on the clamping show (4). 3. Raise    the    hammer    (5)    by    squeezing    and releasing the bulb (6). 4. Release  the  hammer  by  again  squeezing  the bulb and observing its rebound. 5. Several tests should be made at different points of a specimen, and an average reading taken to reduce visual error. 8-21.  TENSILE TESTING.  The terms tension test and compression  test  are  usually  taken  to  refer  to  tests  in which  a  prepared  specimen  is  subjected  to  a  gradually increasing  load  applied  axially  until  failure  occurs.    For the  purpose  of  tensile  testing  implied  by  this  technical order this type of setting would apply to determining the mechanical  properties  desired  in  a  material.    For  this test,   the   following   test   specimens   are   listed.      (See Figure 8-7.) This does not exclude the use of other test specimens  for  special  materials  or  forms  of  material. The tensile strength shall be determined by dividing the maximum load on the specimen during a tension test by the original cross-sectional area of the specimen. 1. Diameter of the reduced section may be smaller at center than at ends.  Difference shall not exceed 1% of diameter at ends. 2. When an extensometer is required to determine elastic properties, dimensions C and L may be modified. In all cases the percentage of elongation shall be based on dimension G. 3. The  type  R₁  test  specimen  is  circular  in  cross section   and   is   used   for   bars,   rods,   forgings,   plates, shapes,  heavy-walled  tubing,  and  castings.    Types  R₂, R₃,  R₄,  &  R₅  are  circular  in  cross-section  and  are  used for material of dimensions insufficient for type R₁. 1. The ends of the reduced section shall not differ in width by more than 0.004 inch. 2. The ends of the specimen shall be symmetrical with  the  center  line  of  the  reduced  section  within  0.10 inch. 3. When  material  is  over  2  inches  thick,  machine to  3/4  inch  or  use  type  R₁  test  specimen.    For  more detailed    information,    refer    to    Federal    Test    Method Standard No.  151. 8-22.  DECARIURIZATION MEASUREMENT. 8-23.      Decarburization   is   the   loss   of   carbon   at   the surface of ferrous materials which have been heated for fabricating,   welding,   etc.,   or   when   heated   to   modify mechanical properties.  Effective decarburization is any measurable   loss   of   carbon   content   which   results   in mechanical  properties  below  the  minimum  acceptable specifications    for    hardened    materials.        The    most common methods used to measure decarburization are microscopic,  hardness  and  chemical.    The  microscopic method  is  sufficiently  accurate  for  most  annealed  and hot rolled material for small amounts of decarburization in high carbon (over 0.60%), high hardness steels. 8-8