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Appendix A – The NORMIN Method (Bore and Spindle)
The NORMIN method was developed by
Hamar Laser Instruments as a way of
compensating for laser or target mounting
errors in bore or spindle work. The word is a
contraction of “NORMal-INverted,” which
briefly describes the method. It is similar to
the four clock readings taken with dial
indicators but uses a laser and a target
instead. The NORMIN method is used in
conjunction with simple fixtures and targets
that allow inexpensive, precision measure-
ment. The target/fixture is set in the bore or
spindle in the NORMal position (cable down)
and the readings are recorded. Then the
target/fixture is rotated 180 degrees to the
INverted (cable up) position, and a second set
of readings is obtained. The two sets of
readings cancel out centering errors and
provide a very accurate result.
There are three centers involved in bore
alignments: True Bore Center, Target Center,
and Laser Reference Centerline. If mounting
fixtures were perfect, the Target Center
would be located at the True Bore Center, and
if perfectly aligned, the True Bore Center
would be located at the laser beam center.
However, they seldom line up. An example
of the three centers with respect to one
another is shown in Figure 18.
Two relationships can be calculated from these three centers and two sets of NORMIN readings: Target Sensor
Concentricity Error (TSCE) and True Bore Misalignment (TBM). The True Bore Misalignment (TBM) is used when it is
desirable to know the true bore centerline position relative to the laser beam center without fixture errors. Usually, the
laser beam center is where a bore center
should
be located, and the TBM shows its
actual
location. The Target Sensor
Concentricity Error (TSCE) is used if the operator wants to place the laser beam center exactly in the middle of a bore.
The general rule: buck in to the TSCE and measure the TBM.
Figure 18 -- Three centers of bore alignment
Summary of Contents for L-702
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