The optical micrometer is used when reading an optical tooling scale. By turning the micrometer knob beside the telescope, the Plano parallel glass plate mounted in front of the objective lens is tilted. The objective is to tilt the parallel plate until the horizontal crosshair of the telescope is positioned between a particular pair of scale divisions. The amount of displacement is read off by observing a linear glass scale through the micrometer reading eyepiece.
The maximum micrometer reading is 0.500 inch. Each graduation of the micrometer scale represents 0.001 inch, with number markings every 0.010 inch up to 0.500 inch.
To read a given level value the following steps are taken:
INDEX POINT BELOW LOS SCALE READING + MICROMETER READING = 1.600 in. + 0.045 in.
DISTANCE BETWEEN INDEX POINT AND LOS = 1.645 in.
- Set up and level instrument.
- Adjust the micrometer knob until the scale reading in the micrometer reading eyepiece is set to zero.
- Index optical tooling scales on points to be leveled.
- Rotate telescope about the vertical axis until one scale is viewed through telescope eyepiece.
- Tighten horizontal clamp screw.
- Bring split bubble into coincidence with the tilting screw.
- Adjust the horizontal tangent screw until the horizontal crosshair is superimposed over the desired vertical line of graduations.
NOTE: The scale markings are separated in intervals of 0.100 inch each. When rotating the micrometer knob clockwise, the scale will appear to move downward.
- Rotate the micrometer knob on the right side of instrument until the horizontal line of the reticule is positionedexactly between two graduations.
- When reading from an index point that is located below the level line-of-sight, the micrometer reading added to the scale reading is the total distance between the index point and the line-of-sight.