HAMAR LASER L-705, 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 conjunc-
tion with simple fixtures and
targets that allow inexpen-
sive, 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
errors 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 21.
Two relationships can be calculated from these three centers and two sets of NORMIN readings: the
Target Sensor Concentricity Error (TSCE) and the 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 is: buck in to the TSCE and measure the TBM.
Figure 21 -- Three centers of bore alignment