Registering Gauge
The registering gauges shown in the illustrations are two of the best examples of this class of tools. They are manufactured by A. J. Logan, Waltham, Mass., and are very accurate and nicely finished. Fig. 142 is a an upright and jaw gauge. and Fig. 143 is designated as a jaw and depth gauge. They are both made to gauge one one-thousandth of a centimeter or one-thousandth of an inch.
Fig. 143 shows the piece of work marked A, being gauged, while B represents a stationary spindle to get the depth of a hole or recess or the thickness of any piece of work which will be indicated on the dial. Fig. 144 illustrates a millimeter gauge which is a favorite with the watchmaker. It will register to one-tenth of a millimeter, and is especially useful in getting the depth, width and thickness of main-spring barrels. This gauge, which was invented by Moritz Grossmann, was by him made with great care, but in late years it has been made by a German manufacturer of tools, who is not noted for extreme accuracy. This gauge has a millimeter scale on each side, and when the vernier side is brought to the extreme end, as in measuring depths, it often happens that the zero marks cannot be made to correspond when the two ends are flush. To correct this, set the zero of the vernier slide to correspond with the zero on the large scale and then be means of a copper lap on the lathe and some carborundum powder, the two ends may be ground off at right angles and to coincide with one another. This gauge is hardly light enough for measuring pivots and balance staffs while working on them in the lathe. In fact there is no gauge as yet on the market which can be considered ideal for this purpose. A gauge for this purpose must be extremely light and at the same time must be very accurate.