Machinery's Handbook, 31st Edition
CALIBRATION OF VERNIER, DIAL AND DIGITAL CALIPERS 801 Table 19. Equipment Requirements and Minimum Accuracy Specifications of Required Standards Table 19. (Continued) Equipment Requirements and
Recommended Measurement Standards
Minimum Use Specifications
Noun
Alternative
Range: 0–1.0000 inch 0–25 mm
Precision Micrometer
Mitutoyo Series 293
Starrett No.3732 Precision Ground Pin or Ball ± 40 in / 0.001 mm Mitutoyo 517-808
Precision Pin or Ball 0.500 inch / 12 mm Van Keuren Class XX
Range: 24 x 36 Accuracy: Grade A
Starrett Crystal Pink EDP 80655
Surface Plate
Note: Standards listed are recommended and are determined to meet the necessary accuracy requirements of the calibration process. Substitute or alternative standards may be used as long as they have a current in tolerance calibration status and have been determined to meet or exceed the minimum accuracy specifications as listed in Table 19. Note: Special care should be taken to clean and apply protective coating when handling gage blocks or other precision standards with bare hands. The use of clean cotton or vinyl gloves is recommended to prevent corrosive oils from damaging precision surfaces. Vernier, Dial and Digital Caliper Calibration Process.— The temperature of the cali bration environment must be maintained at approximately 23° C with a fluctuation in temperature of no more than ± 0.1° per hour. Table 20. Range and Tolerance Limits Feature Method
Range (inch)
Accuracy (inch) ± 0.0005
Determined by observation of scale Measured with Precision cylindrical plug gage
Scale Zero
Set at Zero
Jaw Parallelism
0.00–0.250
± 0.001 inch
0 to 6.000–0.250 0 to 9.000–0.300 0 to 12.000–0.300 0 to 24.000–0.300 0 to 36.000–0.500 0 to 48.000–0.500
(inch) +0.000 - 0.005
ID Jaws (Nibs) Set at Scale Zero
Measured with precision micrometer
0–6.00 inch 6–24 inch 24–48 inch 0–6.00 inch 6–24 inch 24–48 inch
Determined at 4 equal points along the main scale by direct comparison with gage blocks
± 0.0010 inch ± 0.0020 inch ± 0.0030 inch ± 0.0010 inch ± 0.0020 inch ± 0.0030 inch
Outside (OD) Jaws
ID Jaws (Knife Edge)
Measured with gage blocks
Depth Rod
0.000–6.000 inch
± 0.001 inch Measured with gage blocks Note: Metric equivalents apply to all tolerance limits stated in Table 20. All tolerances based on AFMETCAL, NAVAIR and GGG-C-111guidelines and specifications. Default to manufacturers specifications if different from those represented here. Nib Calibration, Inside Measurement, Type 1.— Class 1, 2, and 3: The Total Nib Width (measured to the fourth place) shall be measured over both nibs with the jaws fully closed as shown in Fig. 28. The offset value shall be marked on the Inside Measurement side of the sliding jaw or main beam and on both sides of the main beam of the Type 1, Class 3.
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