TM 9-243READING A STANDARD MICROMETERReading a micrometer is only a matter of reading themicrometer scale or counting the revolutions of thethimble and adding to this any fraction of a revolution.The micrometer screw has 40 threads per inch. Thismeans that one complete and exact revolution of themicrometer screw (1) moves the spindle (2) away fromor toward the anvil (3) exactly 1/40 or 0.025 inch.The lines on the barrel (4) conform to the pitch of themicrometer screw (1), each line indicating 0.025 inch,and each fourth line being numbered 1, 2, 3, and soforth.The beveled edge of the thimble is graduated into 25parts, each line indicating 0.001 inch, or 0.025 inchcovered by one complete and exact revolution of thethimble. Every fifth line on the thimble is numbered toread a measurement in thousandths of an inch.TO READ A MEASUREMENT AS SHOWN ABOVE.Read highest figurevisible on barrel (5) . . . . . . . . . . . . . . . . 2 = 0.200 in.Number of lines visiblebetween the No. 2 andthimble edge (6) . . . . . . . . . . . . . . . . . . . 1 = 0.025 in.The line on the thimble thatcoincides with or has passedthe revolution or long linein the barrel (7). . . . . . . . . . . . . . . . . .16=0.016in.TOTAL= 0.241 in.7-4
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