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Inside a watch, clock or mechanical instrument, the gears are often carried on shafts whose ends are often turned down to a much smaller diameter where they run in the supporting plates - this reduced section is known in watchmaking parlance as pivot. As the pivots needs to have a very smooth surface - and also need reconditioning from time to time - a technique has been evolved (used by watchmakers for almost as long as their trade has existed) called pivot polishing (or more correctly burnishing). The operation can also be carried on other rotating surfaces within the assembly, both cylindrical and tapered, and ensures that the instrument runs with the minimum of friction, an important consideration in any fine, delicate mechanism.
Normally undertaken by skilled handwork with a file and flat burnishing tool, an alternative is to use a high-class, professional machine like the Hauser where the process is more akin to surface grinding - but instead of a grinding disc, a specially formed carbide or ceramic wheel is used that simultaneously cuts away a tiny amount of material while imparting a mirror-like finish. A further result of the process is that pores in the surface are closed up to provide a thin but tough skin - a homogeneous structure - further reducing friction and extending service life. Depending upon the diameter of the workpiece and length of the pivot, work times vary between 1/2 and 40 seconds with the amount of material removed being minute, usually not more than 0.004" to 0.008" (0.01 to 0.02 mm) on brass and mild or nickel steels and from 0.002" to 0.004" (0.005 to 0.01 mm) on hardened materials. An alternative is a ceramic wheel, in which case material can be removed more quickly - provided that the wheel is sharpened and profiled correctly. The use of these special wheels requires another Hauser machine to sharpen and profile them, either the Type 306 with its single diamond-charged wheel for work on the radius and periphery, or the twin-wheel 244 that can tackle the periphery, face and radii.
Over many years the well-known Swiss Hauser Company made a number of pivot-polishers, some automatic for production work in factories and others intended for use by hand in watch, clock and instrument repair shops. Amongst those offered were the semi-automatic Types 430 and 438 (with and without automatic loading); the basic hand-operated Types 241 and 232; the Type 439, a model with similar main mechanical components to the 241 but with a vertical polishing quill and intended for use in the miniature gear industry; the popular and widely-sold Type 191 and the Type 212, a machine able to simultaneously polish three diameters and shoulders with the polishing quill in either a horizontal or vertical position..
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