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 speed inspection, some of these gauges are now being rough molded of glass by Corning Glass Works and A. H. Heisey & Co., and finished by instrument makers. Glass gauges do not rust, need not be greased when idle (thus avoiding cleaning before use), are not corroded by perspiration or chemical vapors. Glass is lighter than steel, is less affected by the heat of an inspector's hands. Its transparency is an aid in positioning in the delicate handling necessary in such operations. Once the molds are made, glass gauges cost half as much as steel, may also be colored for quick selection.

Curiously, breakage is no drawback: the quick-fingered people who get to be inspectors seldom drop things. In the rare accidents that befall even the quickest-fingered, a dropped steel gauge is useless until recalibrated; a glass gauge either breaks or is as good as new.

*One end will just go into a drilled hole or tube, the other end will not.

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