Oil Sink
The depression around the pivot holes for the purpose of furnishing a supply of oil and also retaining it at the pivots. When the oil sink is in metal which is not gilt and is blackened, if they should be polished out at the time of cleaning it will probably be at the expense of the fresh oil. Pivots should come well through the plate into the sink; if they do not the sink should be deepened. Oil sinks should be deep rather than wide, and well polished. Saunier says that care should be taken that the internal faces of the holes in which the shoulders of the axis rest, as well as the external faces, when these holes are provided with end-stones, are hollowed in tallow drop form, with a very slight interval between the bottom of the hole and the end-stone. When these precautions are taken, the oil, if not present in too great a quantity, will neither spread nor run down the axis, but will remain partly in the oil sink and partly attached to the shoulders of the axis, and in the case of pivot holes with end-stones, as the oil is exhausted, that spread over the end-stone will be drawn into the pivot hole through capillarity.