Gradua ted in One- Thousandth of a Millimeter 0.001MM Reading a 0.001mm micrometer is exactly like reading a 0.002mm micrometer except that there are ten divisions on the vernier occupying the same space as nine divisions on the thimble (Fig. B). Therefore, the difference between the width of one of the spaces on the vernier and one of the nine spaces on the thimble is one-tenth of a division on the thimble, or one-thousandth (0.001mm). First obtain the hundredth of a millimeter (0.01mm) reading. Next, see which of the lines on the vernier coincides with a line on the thimble. If it is the first line add 0.001mm to the reading, if it is the second line add 0.002mm, etc. Only every second vernier line is numbered on a 0.001mm reading tool because of space congestion. FIG. A FIG. A Gradua ted in Hundredths of a Millimeter 0.01MM The screw head pitch is one-half millimeter (0.5mm). One revolution of the thimble advances the spindle face toward or away from the anvil face precisely 0.5mm. The reading line on the sleeve is graduated above the line in millimeters (1.0mm) with every fifth millimeter being numbered. Each millimeter is also divided in half (0.5mm) below the reading line. Two revolutions of the thimble to advances the spindle 1.0mm. The beveled edge of the thimble is divided into fifty equal parts, with each line representing 0.01mm and every fifth line being numbered. Rotating the thimble from one of these lines to the next moves the spindle longitudinally 0.01mm; rotating two divisions represents 0.02mm, etc. To read the micrometer, add the number of millimeters and half-millimeters visible on the sleeve to the number of hundredths of a millimeter indicated by the thimble graduation indicated by the reading line. Gradua ted in Two- Thousandths of a Millimeter 0.002MM Metric vernier micrometers graduated in 0.002mm are used like those graduated in hundredths of a millimeter (0.01mm), except that an additional reading in two-thousandths of a millimeter (0.002mm) is obtained from a vernier scale on the sleeve. The vernier consists of five divisions on the sleeve, which occupy the same space as nine divisions on the thimble (Fig. B). Therefore, the difference between the width of one of the five spaces on the vernier and one of the nine spaces on the thimble is one-fifth or two-tenths of a division on the thimble, or two-thousandths (0.002mm). To read a 0.002mm micrometer, first obtain the hundredth of a millimeter (0.01mm) reading, then see which of the lines on the vernier coincides with a line on the thimble. If it is the line marked "2" add 0.002mm, if it is the line marked "4" add 0.004mm, etc. EXAMPLE: The 5mm sleeve graduation is visible............... 5.00mm One additional 0.5mm line is visible on the sleeve.................................................. 0.50mm Line 28 on the thimble coincides with the reading line on the sleeve, so 28 x 0.01mm......... = 0.28mm The micrometer reading is................................5.78mm FIGURE C – READING 5.008mm The 5mm sleeve graduation is visible............. 5.000mm No additional lines on the sleeve are visible................................................ 0.000mm The reading line on the sleeve lies between zero and the first line on the thimble, indicating that a vernier reading must be added.......................................................... ---- Line 8 on the vernier is the only line that coincides with a line on the thimble........... 0.008mm The micrometer reading is............................. 5.008mm FIGURE C – READING 5.005mm The 5mm sleeve graduation is visible, representing........................................ 5.000mm No additional lines on the sleeve are visible.... 0.000mm The reading line on the sleeve lies between zero and the first line on the thimble, indicating that a vernier reading must be added................. ---- Line 5 on the vernier is the only line that coincides with a line on the thimble........... 0.005mm The micrometer reading is............................. 5.005mm SLEEVE THIMBLE READING 5.78mm SLEEVE FIG. B Reading 5.000mm THIMBLE SLEEVE FIG. C Reading 5.008mm THIMBLE SLEEVE FIG. B Reading 5.000mm THIMBLE SLEEVE FIG. C Reading 5.005mm THIMBLE 23 starrett.com M icrometers