MACHINE-SHOP PRACTICE 



437 



has been moved from the zero point on the bar. We now count 

 upon the vernier the number of divisions, until one is found which 

 coincides with one on the bar. This division will be the number of 

 thousandths to be added to the distance read off the bar. The best 

 way of expressing the value of the divisions on the bar is to call the 

 tenths, one hundred times one thousandth (.100), and the fourths 

 of tenths, or fortieths, twenty-five times one thousandth (.025). 

 The vernier SCALE 



vernier coincides wit*h a line on the bar, thus making six-thousandths 

 (.006) of an inch to be added to the reading from the scale, which 

 would make the total reading one and two hundred and six thou- 

 sandths. (1.206) inch. 



In making inside measurements with a 6 in. vernier, two and 

 one-half tenths, or two hundred and fifty thousandths (.250), of 



an inch and with the 

 12 in. and 24 in. vernier, 

 three-tenths, or three 

 hundred times one 

 thousandth (.300), of an 

 inch, should be added 

 to the apparent read- 

 For determining mg on tne vernier side 

 for the space occupied 

 by the caliper points. With a vernier caliper (Fig. 202) reading 

 to metric measure, add 6 mm. When the other side of the in- 

 strument is used no deduction is necessary, as there are two lines, 

 one indicating inside and the other outside measurements. 



FIG. 202. Vernier Caliper. 



accurately the depth of gear teeth. 



506. Thickness Gauge. The thickness of metal may be 

 determined by means of a thickness gauge, which consists 



