Machinery's Handbook, 31st Edition
CALIPERS, VERNIER AND DIAL 785 additional 0.0003 inch shall be acceptable with no total tolerance accumulated within any single foot of main scale length. All graduations within any 1 inch increment shall be accurately located in that inch increment within 0.0002 inch. Vernier Scale : The inch vernier scale shall be divided into either 25 minor divisions each equivalent to one twenty-fifth of the main scale minor division or twenty five thousandths of an inch or 50 divisions each equivalent to one fiftieth of the main scale minor division or fifty thousandths of an inch. On either scale each alignment of the vernier scale mark to the main scale is equivalent to one thousandths of an inch. The graduated length for the 25 division inch graduated vernier scale shall be either 0.6000 or 1.2250 inch ± 0.0002 and are divided into 25 equal increments accurately spaced to within ± 0.0002 inch. All graduations shall be of a length so as to be easily discernible with the graduations for 0 (zero) and each 0.005 inch having extra length to enable them to be easily distinguished. The 0 (zero) index and each 0.005 inch increment shall be clearly marked with the incremental value. The vernier scales that are divided into 50 increments shall have a length of either 1.225 or 2.450 ± 0.0002 with each increment accurately spaced to within 0.0002 inch. Each instrument shall be marked with the scaled value. Metric Graduated Instruments.— Main Scale: The metric graduated instruments will be graduated to read in 1/50 mm (0.02mm) increments. Each centimeter of the main scale shall be represented with a graduation mark representing the incremental value. For instruments with 25 increment vernier scales, the main scale shall be graduated in centi- meters, millimeters and half-millimeters. Each centimeter segment shall be subdivided into ten increments of 1 millimeter each. Each 1 millimeter increment shall be further divided into 2 increments of 1 ⁄ 2 millimeter each for 20 divisions per centimeter. Centime- ters shall be numbered from zero with easily read numerals. The graduation lines for cm, 1 ⁄ 2 cm, mm, and 1 ⁄ 2 mm shall have length of descending order. All graduation lines shall be clearly marked as described in the previous Scale and Graduations and Inch Graduated Instruments sections, and be easily readable under normal operating conditions. Instruments with 50 increment vernier scales shall have the main scale graduated in centimeters and millimeters with half-millimeters at the manufacturers’ option. Each graduation of the main scale within the first 30 cm shall be accurately located to the reference zero index within 0.008 mm. With each additional 30 cm length of the main scale and additional 0.008 mm shall be acceptable with no total tolerance accumulated within any single 30 cm of main scale length. All graduations within any 1 cm increment shall be accurately located in that centimeter increment within 0.005 mm. Vernier Scale: Vernier scales for metric instruments divided into 25 increments shall have a graduated length of 12 mm or 24.5 mm, ± 0.005 mm and scales divided into 50 increments shall have a graduated length of 24.5 mm or 49 mm, ± 0.005 mm.
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0.02 mm
Fig. 19. Common Metric Vernier Caliper Scale Markings The metric vernier scale most generally found in the current market shall be divided into 10 divisions or 0.1 mm, each division further divided into 5 minor divisions equivalent to a resolution of 0.02 mm. The spacing and location from zero shall be accurate to within 0.005 mm. All graduations shall be of a length so as to be easily discernible with the graduations for 0 (zero) and each 0.1 mm having extra length to enable them to be easily
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