1...Gage indicating applied pressure
2. Hydraulic actuating unit
3. Lever for applying pressure
4. Hardened steel ball
5. Elevating screw
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.)
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.
Do not perform test closer than
1/8" from edge of specimen to
assure accurate reading.
Select the proper anvil and penetrator and place
proper weight on the weight pan.
Check trip lever for proper location. Lever
should be located in the OFF LOAD position.
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,
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.
Apply the major load by tripping the trip lever.
Trip the lever, do not push.
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