Machinery's Handbook, 31st Edition
INSIDE MICROMETERs WITH JAWS 777 be numbered 0, 9, 8, … 3, and 2 for the 0.200 to 1 inch range inside micrometer; and 15, 14, 13, … 6, and 5 for the 0.500 inch through 1.5 inch range inside micrometer. The numerals for graduations on the thimble shall read in the opposite direction from those on a conventional Type I OD micrometer. Measuring Faces: The measuring faces on the Type II, Class 1 inside micrometer shall two jaws in the vernier-caliper style designed to be perpendicular to the axis of travel of the micrometer spindle and shall have a radius of curvature no greater than 1 ⁄ 2 the diameter if the smallest value of the measuring range. The measuring surfaces shall conform to all design and accuracy requirements defined in the previous section, Type I, Caliper Micrometer . Type II, Class 2, Rod and Sleeve.— The Type II, Class 2, Rod and Sleeve Inside Micrometer shall follow in design as shown in Fig. 13. The ranges and accuracy shall follow Table 4. The micrometer head is calibrated separately from the length rods and maintains a separate calibration tolerance as shown in Table 4.
3
4
Rod
0 1
0
20
Spacing Collar
Micrometer Head
Means for Attaching to Head
Handle
Fig. 13. Type II, Class 2: Inside Micrometer: Rod and Sleeve Design Table 4. Type II, Class 2, Inside Micrometer Accuracy Tolerance Inch Metric
Tolerance
Tolerance
Range (inch) 1 to 2 2 to 8 2 to 12 8 to 32 8 to 36
Range (mm) 1 to 2 25 to 50 50 to 200 50 to 300 200 to 900
Micrometer Head (inch)
Length Rods (inch)
Micrometer Head (mm)
Length Rods (mm)
0.0002 0.0002 0.0002 0.0002 0.0002
0.0003 0.0004 0.0005 0.001 0.001
0.0002 0.005 0.005 0.005 0.005
0.0003 0.0075 0.010 0.0125 0.025
Design: The Type II, Class 2 inside micrometer shall essentially consist of a micrometer head, measuring (length) rods, spacing collars, a knurled locking screw to secure micrometer head in place after obtaining measurement and an extension handle in some designs to optimize handling of unit in deeper bores or smaller diameters. Micrometer Head : The micrometer head consists of a micrometer screw barrel and thimble graduated in design as defined for the Type I outside micrometer (see Graduations on page 767) with the exception of the vernier lines.
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