Registering Gauge
American Watchmaker and Jeweler (1892)
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.
What Has Changed in the Last Century
When the American Watchmaker and Jeweler described these tools in 1892, the best available were mechanical dial and vernier gauges reading to a thousandth of an inch or a tenth of a millimetre, and the writer complained that "there is no gauge as yet on the market which can be considered ideal" for measuring pivots and balance staffs in the lathe. The instruments themselves survive almost unchanged in form: bench micrometers and dial indicators of this pattern are still sold to watchmakers, and Moritz Grossmann's millimetre gauge is echoed in the Bergeon and Jacot-style gauges on modern benches. What has changed is the readout and the resolution. Digital calipers and micrometers with electronic scales now give thousandths of a millimetre directly, and the delicate work the 1892 writer found impossible to gauge is handled by non-contact optical and laser measuring systems that touch the pivot not at all.
Written for this edition, 2026.