Figure 2-31.--Riehle portable hardness tester.
The hardness reading is based on the measurement
small knurled knob below the clamp. The larger
of the additional increment of penetration produced by
diameter knob, extending through the slot in the side of
applying a major load after an initial penetration has
the clamp, is used for actual clamping.
been produced by the minor load. In reporting a
Each Riehle tester is supplied with a diamond
hardness number, the number must be prefixed by the
penetrator and a 1/16-inch ball penetrator. The ball
letter indicating the scale on which the reading was
penetrator should not be used on materials harder than
B-100 nor on a load heavier than 100 kilograms. This is
to avoid the danger of flattening the ball.
Removal and Replacement of a Penetrator
The diamond penetrator, when used with a
The penetrator is retained in the tester by means of
150-kilogram load, may be used on materials from the
a small knurled clamp screw extending from the top of
hardest down to those giving a reading of C-20.
the upper clamp. To remove a penetrator, there should
When the expected hardness of a material is
be at least 2 or 3 inches of space between the upper and
completely unknown to the operator, it is advisable to
lower clamps so that one hand can be placed
take a preliminary reading on the A scale as a guide in
underneath the upper clamp to catch the penetrator
selecting the proper scale to be used.
when it is released. Two or three turns of the clamp
screw will release the penetrator. The two contact pins
that extend through the penetrator on either side of the
point are retained in the tester when the penetrator is
The basic procedures for making a test with the
Riehle tester are as follows:
To replace a penetrator, it must be turned so that the
1. Apply a minor load of 10 kilograms.
flat side faces the clamp screw, and the locating pin on
2. Set the penetration indicator to zero.
the penetrator is in line with the slot provided to take the
pin. The contact pins should be guided into their
3. Apply a major load of 60, 100, or 150
respective holes through the penetrator. With the
kilograms (depending on the scale), and then reduce the
penetrator in place, it should then be clamped securely
load back to the initial 10-kilogram load.
by turning the clamp screw. Before you make an actual
4. Read the hardness directly on the penetration
test, one or two preliminary tests should be made to
properly seat the penetrator.