The stern tube is normally made of cast iron slightly larger at the forward end to ease removal. The forward end is flanged and bolted to a doubler plate stiffened aft peak bulkhead. The forward end is supplied with a stuffing box and gland, the after end with a bearing comprising lignum vitae or similar, the wood is dove tailed into a brass bush, the wood is machined and cut on end grain. Can be lined with Lignum Vitae , rubber composition (cutlass rubber) or an approved plastic material (Certain plastics possess good bearing properties being inert and very tolerant of slow speed boundary lubrication conditions. Cresylic resin bonded asbestos such as Railco WA80H give good results in condition of heavy water contamination in the lubricating oil of almost 100%)

       There are two kinds of lubrication systems for the stern tube: water lubrication and oil lubrication

        For water lubricated bearing not less than 4 x the diameter of the steel shaft. If the bearing is over 380mm diameter forced water lubrication must be used, a circulating pump or other source with water flow indicator.