PRECISION TOOL MAKING 



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rately lapped surface plate of the instrument and brought into contact 

 with the vertical plunger, which operates the universal dial indicator 

 through a lever arrangement. The movement of the pointer is about 

 1/16 in. for each .0001 in. vertical movement of the dial plunger. By 

 noting the difference between the dial reading for a standard gage block 

 of the size required and the part being measured, a comparison between 

 the two may be made to within .0001 in. and by interpolation between 

 the calibration marks to within a few hundred-thousandths of an inch. 

 The universal dial indicator is also frequently used by the tool maker 

 with a standard surface plate, and a suitable arm for holding the indica- 

 tor, when checking work in process. 



Fig. 23 — Precision measuring instrument with fluid gage and "Hoke" 

 gage block set. 



If greater accuracy is required, parts are sometimes measured by 

 comparison with the standards, using the liquid gages shown in Figs. 

 23 and 24. The instrument in Fig. 23, which has a multiplying ratio 

 of 2200 to 1, was made in the Hawthorne Works Tool Room, while the 

 other is a commercial liquid gage or prestometer. However, the 

 comparator most generally used at present for this class of work is the 

 optimeter shown in Fig. 25. This instrument makes use of an optical 



