Extremely handy for use in grinding and setting screw cutting tools, these gages meet the following standards: American National or US 60o, Whitworth or English 55o and Metric 60o. They also have a useful scale for finding the number of threads per inch through graduations in 14ths, 20ths, 24ths and 32nds of an inch on C391 and C396. Graduation on C398M are in mm and 1/2mm. C391 has a table of double depths of threads for determining size of tap drills. Made of spring-tempered steel with satin chrome finish. Gaging surfaces ground.
