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Bore Alignment

The L-705 was designed to reduce the amount of targets used when performing bore alignment. Traditionally, bore alignment was accomplished with a reference system, like optics, that uses two reference targets mounted in two reference bores. The L-705's laser beam is concentric to its housing to within .0005" and thus can be used as one of the reference targets. As a result, the L-705 Laser Borescope usually needs only one target to perform alignments.

To perform alignments, the L-705 laser is fixtured into one end of the reference bore. Next, a target (T-218 or A-510) is inserted into the far end of the initial reference bore or into a second reference bore. Target fixturing can consist of a 3-legged, spider-type fixture with a flange adapter (T-225) or a 4-legged, self-centering adapter (A-510A).

The laser's vertical and horizontal angles are adjusted using built-in micrometers so the target in the far reference bore reads zero (.000" or .0000"), both horizontally and vertically. Then the laser is rotated 180 degrees and the NORMIN procedure is followed to determine centering error offsets in the laser setup. After subtracting the offsets, the laser should then be colinear to the centerline, as defined by the two reference bores. This process can be greatly simplified with our Read8 or Bore6 software.

The NORMIN Method : The Relationship of Three Centers - Bore Alignment The target is then placed in the desired bore for measurement, and once properly centered, the readings display the bore misalignment. However, this is a measure of the bore centering error only. To truly align a bore to a centerline, two sets of readings (vertical and horizontal) are needed: one set in the section of the bore closest to the laser and one set in the section farthest away from the laser. The average of these two sets of reading indicates how far off center the bore is to the reference bores. The difference between the readings is how much angle the bore has to the reference bore centerline. To align bore, both bore sections must be adjusted to zero (.000" or .0000"), an easy task given that the readings from the target are live.

The straightness of a single bore can easily be checked without having to use the NORMIN procedure, as long as an alignment is not required. Simply fixture the laser in one end of the bore and place our self-centering target (A-510) in the other end. Adjust the laser so the readings are zero (.000" or .0000") and start taking measurements. The A-510 target uses a pole to push and position the target into each measuring point, and can take measurements up to 30' into a bore.

Any slope error due to the laser not being perfectly centered is then removed from the raw reading by using the least-squares best-fit algorithm built into our Read 8 Software. This algorithm removes the slope by finding a line that "best fits" the raw data, and it is especially useful because the laser beam does not have to be exactly centered in the bore to get accurate straightness measurements.

For high-tolerance bore alignment applications, the target centering error (TCE) must be calculated. TCE is calculated by taking two readings, one at the 12 o'clock position and the second at 6 o'clock (horizontal and vertical calculations are done separately). The second reading is subtracted from the first and the result is divided by 2. This is the TCE and shows how far off the center of the target is from the center of the bore. It can then be subtracted from all subsequent bore measurements to get the true misalignment number. Our software programs (Bore 6 and Read 8) can easily calculate TCE and even automatically remove it from the displayed reading.

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