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approximately coincide with the fixed line of the projecting
screen. The difference allowed may be ±5 degree value.
Use the micro-adjustment knob to adjust the zero digit, so as to
keep the base line of the target entirely coincide with the
projecting screen.. If the knob is turned to the limit position, the
two lines are still not able to coincide, then it shall be unloaded,
and turn the micro-adjusting knob to the intermediate position,
and select another point on the test piece, then repeat the above
mentioned operations again.
Push the loading handle forward by turning it clockwise, during
loading, the calibrated line of the target rod which is displayed
on the projecting screen is moving up and down, until the target
rod stops to lower, then start to compute the load holding time
until the load holding time is reached, then pull the handle again
to its original position.
The reading which is the indicating target rod calibrated line on
the projecting screen to the fixed target rod line is the Rockwell
hardness value of the tested specimen.. Lower the screw rod,
make the test piece leave the indenter, move to another position
and repeat the above mentioned test.
The Brinell and Vickers hardness test shall, after the completion of
the above mentioned procedures, move the upper sliding plate and
the test piece together under the microscope, then gradually uplift
the screw rod micro-quantitatively, align it to the focal distance, and
make the image of the indentation distinct, then measure the
diameter of the indentation or the diagonal length of the indentation,
next, look over the attached table and obtain the Brinell or Vickers
hardness value. When purchasing, the surveying microscope which
forms a complete set of the apparatus is not obtained, then you may
carry out the survey by means of your own prepared surveying
microscope.
The computing method of the surveying microscope against the
indentation is as follows:
L -- the diameter of the indentation or the diagonal length in mm.
n -- number of division line measured from the indentation (i.e. the
difference between the first reading and the second reading).
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I -- the minimum calibrated value of the surveying microscopic drum
wheel
It is 0.004 mm when 2.5x objective is used.
It is 0.002 mm when 5x objective is used.
For instance: Use a 5x objective to measure the Vickers indentation
of a 294.2N test force.
The first reading is 221 division line.
The second reading is 400 division line.
According to this indentation:
L = n x l = (400-221) x 0.002 = 0.358 mm.
Look over the attached table, we obtain 434HV
If the Brinell hardness test is carried out, the method of
calculation is identical.
L= n x lxb when test the Brinell hardness.
b--Indenter
coefficient.
When use Ø2.5mm steel ball indenter b is 4.
When use Ø5mm steel ball indenter b is 2.
