TM 9-243 READING A STANDARD MICROMETER Reading a micrometer is only a matter of reading the micrometer scale or counting the revolutions of the thimble and adding to this any fraction of a revolution. The micrometer screw has 40 threads per inch. This means that one complete and exact revolution of the micrometer  screw  (1)  moves  the  spindle  (2)  away  from or toward the anvil (3) exactly 1/40 or 0.025 inch. The lines on the barrel (4) conform to the pitch of the micrometer screw (1), each line indicating 0.025 inch, and each fourth line being numbered 1, 2, 3, and so forth. The beveled edge of the thimble is graduated into 25 parts, each line indicating 0.001 inch, or 0.025 inch covered by one complete and exact revolution of the thimble. Every fifth line on the thimble is numbered to read a measurement in thousandths of an inch. TO READ A MEASUREMENT AS SHOWN ABOVE. Read highest figure visible on barrel (5) . . . . . . . . . . . . . . . . 2 = 0.200 in. Number of lines visible between the No. 2 and thimble edge (6) . . . . . . . . . . . . . . . . . . . 1 = 0.025 in. The line on the thimble that coincides with or has passed the revolution or long line in the barrel (7) . . . . . . . . . . . . . . . . . . 16 = 0.016 in. TOTAL = 0.241 in. 7-4