New Parts for Old—by the Fescol Process
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How Worn Components Are Built Up and Machining Errors Corrected by Electric Deposition Giving Perfect Homogeneity
THE expression, "putting on tool," must, in the past, have worried many an apprentice, but in these days a machine-shop foreman who tried this old saw on the boys might be politely informed of the Fescol process of metal deposition.
The mere depositing of metal on metal is, of course, no new discovery, but when it comes to comparatively heavy deposits of a perfectly homogeneous character. then apparatus and equipment of the most elaborate and expensive nature is called for.
This was revealed to us during a recent tour of the works of Fescol, Ltd., North Road, London, N.7, where is housed what is claimed to be the largest and most modern plant of its kind in the world.
The process is an electrical one, and as the standard supply for the district is 400 volts, single phase, it has to be converted to three phase and turned into low-voltage d.c. as it is heavy currents at low pressure that are required. This, in itself, means the installation of extensive electrical plant.
Whereas the Fescol process is undoubtedly invaluable as applied to the building up of worn components, it is also extensively used in the treatment of new parts, not only with a view to increasing resistance to wear, but as a means for protection against corrosion.
Our interest was in engine crankshafts and camshafts, axle-shaft and propeller-shaft splines, steering king-pins and
other vehicle components which were not only being rebuilt, but which, as a result of treatment, were being given a wearing surface of far greater durability than when originally produced.
Taking a worn spline on an axle shaft as an example, the first stage in the process lies in removing all traces of dirt and grease. The worn spline is then brushed with pumice powder, whilst the rest of the shaft, which has to be protected from electrolyticaction, is covered with beeswax and then the whole shaft is dipped into molten paraffin wax. Later, an operative carefully removes the wax covering on the splines, which, as the result of the application of pumice powder, peels off readily.
The component is then suspended in a vat until the desired amount of metal has been deposited.. If the part has to be machined by Fescol, Ltd., it is then taken to the machine shop, where it is finished to a high degree of accuracy.
All such components have to pass through an inspection department, the character of which is comparable to that installed in up-to-date engineering works.
The outstanding impressions, which one obtained from a tour of the Fescol works, were that every stage in the process is carried through with meticulous care and that any component, however intricate in construction and difficult to process, can be handled with the same facility as, say, a steering king-pin.