HAMAR LASER L-708, Operation Manual

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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 com-
pensating for laser or target
mounting errors in bore or
spindle work. The word is a
contraction of “NORMal-
INverted,” which briefly de-
scribes the method. It is
quite similar to the four clock
readings taken with dial indi-
cators, but uses a laser and a
target instead. The NORMIN
method is used in
conjunction with simple
fixtures and targets that allow
inexpensive, precision
measurement. 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 ob-
tained. The two sets of read-
ings cancel out centering er-
rors and provide a very accurate result.
There are three centers involved in bore alignments: the True Bore Center, the Target Center, and the
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. In reality, 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). 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 is: buck in to the TSCE and measure the TBM.
Figure 16 -- Three centers of bore alignment