American National or U.S. 60º standards
Extremely handy for use in grinding and setting screw cutting tools
Gage also has a table of double depths of threads for determining size of tap drills.
Ground gaging surfaces
Made of spring-tempered steel with satin chrome finish.
Very useful for finding number of threads per inch through graduations in 14ths, 20ths, 24ths and 32nds of an inch.