4
2. OPERATION (CONTINUED)
The indenter point must always be perpendicular to the surface being tested. To maintain
perpendicularity, the leg of the Impressor must be on the same plane as the indenter point, with
both flats of the leg touching the same surface. Irregularlyshaped objects to be tested should be
mounted in a holding jig to assure that perpendicularity is maintained. For flat objects, a tempo-
rary offset of the leg to accommodate the thickness of the part being tested can be obtained by
placement of washers of appropriate thickness between the leg and the case of the impressor.
Without perpendicularity, accuracy of the reading cannot be assured.
Maintenance
The Impressor is a precision mechanical instrument and should always be handled with care. The
deflection indicator built-in to the Impressor has a normal reading of zero when not in use.
The Indenter Point has a tip precisely-machined to very small dimensions. It should be used with
care to prevent damage. Avoid sliding or scraping the Indenter Point when it is in contact with
the surface being tested. If the Indenter Point is damaged, it must be replaced with a new one.
The Impressor ships with two spare Indenter Points.
WARNING
Do not attempt to regrind an Indenter Point when damaged! The mechanical
dimensions of the Indenter Point determine the accuracy of readings
and will create erroneous reading when reground.
To check the condition of the indenter point, first visually inspect it for damage.
Then place the impressor on a hard, flat surface with the appropriate test disk
positioned under the indenter point. Press the impressor handle down firmly, but
carefully, to avoid sideways slippage of the indenter point. The reading on the
indicator should be within the range of values stamped on the test disk. If it is not,
refer to the calibration procedure below.
Replacing the Indenter Point
1. Clean the new indenter with alcohol.
2. Remove the two screws that hold the impressor case halves together (see Figure 1).
3. Lift out the frame while holding the spring sleeve in place (so it will not fall off )
until it can be removed.
4. Loosen the plunger upper guide nut with the provided wrench until the crossnotched
top lip protrudes above the frame.
5. Hold the impressor upside down (so the spring and plunger won’t fall out), then loosen the
locknut with the provided wrench and remove the lower plunger guide.
6. Replace the indenter point in the lower plunger guide, then re-install the lower plunger
guide, leaving about 3/16 of an inch of thread protruding below the frame.
EN
