T.O.  1-1A-9 1...Gage indicating applied pressure 2.  Hydraulic actuating unit 3.  Lever for applying pressure 4.  Hardened steel ball 5.  Elevating screw 6.  Base 7.  Calibrated microscope Figure 8-1.  Brinell Hardness Tester when  using  a  1/16  inch  steel  ball.    A  hardness  value indicated by a number alone is incomplete.  The number must  be  prefixed  with  a  letter  to  indicate  the  load  and indentor used to obtain the number.  There is a variety of combinations of indentors and loads used to obtain a hardness  value  in  accordance  with  hardness  range  of various  material.    The  combinations  are  listed  in  Table 8-2 which is based on Specification ASTM E-18. 8-10.  Review of Table 8-2 will reveal that the Red Dial Numerals   "B"   scale   are   used   for   steel   ball   indentors regardless  of  size  of  ball  or  load  and  Black  Figure “C" scales are used for the diamond penetrator.  When the readings  fall  below  the  hardness  value,  C20  (B98)  the material is considered too soft for the diamond cone and 1/16 inch or larger hardened ball should be used.  The diamond cone must be used for all hard materials (those above  100  on  the  "B"  scale)  as  the  steel  ball  may  be deformed by the test.  If in doubt about the hardness of a material start with the diamond penetrator and switch to the steel ball if the material is below C20-C22. 8-11.      Rockwell   Test   Procedure:   The   procedure   for making  the  Rockwell  test  is  outlined  as  follows:  (See Figure 8-2 for machine illustrations.) 1. Prepare the sample by removing (file, grind and polish)  scale,  oxide  films,  pits,  variations  and  foreign material   that   may   affect   the   reading.      The   surface should be flat, of one thickness and no bulge should be opposite the indentation. NOTE Do   not   perform   test   closer   than 1/8"   from   edge   of   specimen   to assure accurate reading. 2. Select the proper anvil and penetrator and place proper weight on the weight pan. 3. Check   trip   lever   for   proper   location.      Lever should be located in the OFF LOAD position. 4. Place  the  test  specimen  on  the  anvil  and  by turning  the  hand  wheel,  raise  it  slowly  (do  not crash) until contact is made with the penetrator. On the older model continue turning until pointer of the indicator has made three revolutions and is  within  five  divisions  (plus  or  minus)  of  the upright   position.      On   the   newer   model   after contact,  continue  turning  hand-wheel  until  the small  pointer  is  nearly  vertical  and  slightly  to right of the dot.  Then watching the long pointer, raise specimen until long pointer is approximately upright within three degrees (plus or minus) of C-O.  If the C= +3 degrees position is overshot, lower the specimen and start over. When the pointer is within three divisions of C- O, set dial to zero.  After this step is complete, the minor load has been applied. 5. Apply  the  major  load  by  tripping  the  trip  lever. Trip the lever, do not push. 6. When  the  trip  lever  comes  to  rest  and  there  is no  further  movement  of  pointer,  return  lever  to the   original   position   and   read   the   hardness number indicated by the dial.  When dial pointer indicates    a    fraction,    use    next    lower    whole number for the reading. 8-12.    All  hardness  tests  should  be  made  on  a  single thickness  to  obtain  accurate  results.    In  testing  curved specimens, the concave side should face the indentor; if reversed,    an    inaccurate    reading    will    result    due    to flattening of the piece on the anvil.  Specimens that do not balance on the anvil because of overhang should be properly  supported  to  obtain  accurate  readings  and  to prevent damaging the penetrator.  Also to obtain a true Change 17  8-3