Science: Glass Yardsticks

Quietest weapons in the U.S. arsenal are the plug, snap and ring gauges which make possible mass production by guaranteeing the accuracy that permits interchangeable parts. Plug gauges, for checking inside diameters, are accurate cylinders frequently with go and no go ends.* One form of snap gauge looks like the letter C and external dimensions are checked in its fixed opening. Ring gauges look like the letter O, are often used in go and no go sets for checking the external diameters of rods, gun barrels and the like.

To save the high-quality steel normally used for such precision instruments, and to...

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