First the old white metal (babbit) is being molten out of the steel bearing tube. The most important part of any remetalling job is the preparation of the surface of the bearing shell or tube. The surface has to be absolutely clean and oil free, in order to ensure an adequate bonding between the steel of the tube and the white metal.
After cleaning the tube is being put in an electric oven for the night at about 400 degrees C. This removes any traces of oil from the surface. The next step is the tinning pot, where the tube surface is covered with a thin layer of white metal. This step is crucial for an even bonding. Finally the tube is put in the remetalling machine, where the main layer of white metal is applied.
Now the bonding between steel and white metal has to be checked. We use an ultrasound measuring device, which can detect any ‘gaps’ between the steel tube surface and the white metal layer. In order to provide a smooth surface for the ultrasound probe, the inside of the stern tube bearing is machined close to the nominal diameter on a horizontal boring machine.
When everything is found in good order, the bearing is finished to nominal size. At present we can handle stern tube bearings up to a length of 2.2 meters.