Machinery's Handbook, 31st Edition
CALIBRATION OF VERNIER, DIAL AND DIGITAL CALIPERS 805 5) Measure the remainder of the length of the UUT at 25, 50, 75, and 100 percent of full scale. Select the appropriate gage blocks and assemble as illustrated in Fig. 30. Measure each test point and record all readings. Calibration of Depth Rod.— 1) Select a 1.000 inch gage block and position it on the sur face plate with the measuring surface against the plate. 2) Close the caliper jaws completely and place the end of the mail beam flat on the surface plate in a vertical position. Apply slight downward pressure bringing the depth rod in contact with the surface plate. Zero the dial or display at this point. a) Type 1 Class 1 calipers do not have depth measurement capability. b) Type 1 Class 2 have a depth rod that is directly tied to the Vernier Scale. If the Zero Reading is OOT (out of tolerance) at this point the depth rod will require service or replacement.
Gage Blocks
Surface Plate
Fig. 31. Caliper Depth Rod Extended through Center Relief Hole of Gage Block. 3) Place the caliper depth rod through the center relief hole of the gage block and extend the rod to make contact with the surface plate as shown in Fig. 31. Assure that the end of the main beam is seated squarely on the surface of the gage block. Apply gently downward pressure with the thumb wheel until contact on the surface plate is felt. Using the thumb wheel, lift the depth rod and re-apply contact to repeat the measurement. Confirm the measurement repeats before accepting. a) Alternately, the depth rod can be extended down the outside of the gage block while in direct contact with the outer surface. The end of the main beam is squarely in contact with the surface of the gage block. This method can be used with a rectangular gage block that has no center relief hole or to assure a square contact between the end of the main beam and the depth rod. 4) If the depth rod is determined to be within tolerance, proceed to the next section, Calibration of Step Height . If the depth rod is found out of tolerance, continue through
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