Use of Gages - Continued
Figure 4-8. Micrometer Barrel
The graduations on the thimble illustrated below, (fig. 4-9), further divide the indications into single
thousandths of an inch by indicating each twenty-fifth of a revolution of the thimble. Therefore one
twenty-fifth of a revolution of the thimble opens or closes the micrometer 0.001 inch (1/1000 inch).
When the micrometer is in the fully closed position, the edge of the thimble coincides with 0 on the
barrel, and 0 on the thimble coincides with the revolution line. Each time a graduation on the thimble
passes the revolution line on the barrel, the micrometer opens 0.001 inch.
Figure 4-9. Graduated End of Thimble