Operation:
This sectional view shows the basic design principle
of the Webster Hardness Tester. The different models vary only in
penetrator and load spring design. These combinations give the ability
to test a wide range of hardnesses and metals.
The penetrator housing, which contains the penetrator and load spring,
slides vertically in the frame of the tester when pressure is applied to
the handles. Only sufficient pressure is needed to "bottom" the lower
face of the housing against the work. Resistance of the work to the
penetrator causes the penetrator to recede into the housing against the
spring pressure. The degree of penetration on the test specimen is
indicated on the dial indicator sitting on top of the housing assembly.
The load can be varied by adjusting the nut above the load spring,
permitting the dial reading to be easily corrected against a test block
of known hardness.
A penetration of 0.010 inch produces a full scale reading on the dial
indicator. Therefore materials in the softer hardness range should be of
sufficient thickness so that the anvil will not influence the test and
produce an "anvil effect
Different models:
Webster Hardness Testers are available in the
following three models:
Model B for Aluminium Alloys
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The Model B Tester is designed to cover
the hardness of aluminum alloys from the 1100 to the 7075 series.
The 20 graduations on the Webster dial indicator covers the range
between 25 and 110 on the Rockwell E scale.
The graphs on this page show the range covered by
the Model B Tester. The lines for these graphs were derived from
many tests on a variety of alloys and show an average curve.
Production lots of alloys can vary in work-hardening characteristics
which may result in instances where readings do not fall precisely
on the curve. All tests were conducted with the Model B Tester set
to read 16 on a standard test strip of 6061-T6 aluminum alloy of
Rockwell E 90± 1 hardness. |
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Model B-75 for Brass and Mild Steel
The Model B-75 Tester was developed to obtain
more sensitive response to slight changes in the upper range of hardness
covered by the Model B. This sensitivity is particularly useful in
testing mild steel and the stronger aluminum alloys. For brass the B-75
covers the range from annealed to full-hard. This added sensitivity is
accomplished by incorporating a penetrator of slightly different contour
and a heavier load spring than used in the Model B. The 20 graduations
on the Webster dial indicator covers the range between 20 and 100 on the
Rockwell B scale.
The graphs on this page show the range covered by the Model B-75 Tester.
Results were derived from many samples, and show the average curve. All
tests were conducted with the Model B-75 Tester set to read 5 on a
standard test strip of 6061-T6 aluminum alloy of Rockwell E 90± 1
hardness.
Model BB-75 for Copper
The Model BB-75 Tester was developed to answer
the need of certain industries for a method of rapidly testing the
hardness of electro-deposited copper and copper in the low hardness
range. The B-75 penetrator is used to give sensitivity and the Model B
load spring is employed to give light pressures. This combination allows
the user to test the soft range of many common materials. The graph
below shows the range covered by the Model BB-75 Tester on copper.
Results were derived from many samples, and show the average curve. All
tests were conducted with the Model BB-75 Tester set to read 17 on a
standard test strip of 6061-T6 aluminum alloy of Rockwell E 90± 1
hardness. REMARK : Beware
of Imitation Product !
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