Machinery's Handbook, 31st Edition
730
Surface Plates
North Side
5
Data Table IV Autocollimator position 2
Line 3
7–8
2–4
Data Table VIII
Data Table VI
Data Table VII
Data Table IX
Line 8
Typical stationary mirror position
8
5
Data Table V
Line 4
2
7
4
Surface Plate
Fig. 4. Turning Mirror Placement for Remaining Lines: TO 33K6-4-137-1 Interferometer Calibration (Ref TO 33K6-4-10-1 30 April 2006).— Calibration of a surface plate can also be accomplished using a laser interferometer. The laser offers the absolute lowest uncertainty in the calibration process, and, although it takes more time than either of the other methods, it is sometimes required by some customers doing military or government contract work. There are several models and methods available on the market today. The general process will be covered, but familiarity with the particular model being used is necessary to complete the full calibration procedure. The process is much the same as the autocollimator calibration method using turning mirrors. The laser tripod and laser head are located as close to the line being shot as possi ble. Move the tripod and realign the laser interferometer for each line during calibration. If available, use the turning mirrors to facilitate the alignment of the beam. As with any high- precision physical measurements, air currents and vibrations will affect the indications. Take precautions to minimize these affects. Clean the surface plate twice with surface plate cleaner and once again with ethyl alcohol prior to beginning the calibration process. Mark the surface with lines as shown in Fig. 5 below. The lines will be either 3 or 4 inches away from the edge of the surface plate, depending on the size of the plate. The North side of the plate will always be the side bearing the manufacturer’s label or the previous calibration label. TI MFG or Certification Label (North Reference)
Fig. 5. Reference Lines for Union Jack 1
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