September 20th, 2010
To get a good finish on any electroplating job – i.e. a component to be chrome, gold or silver plated - good preparation, using a variety of Metal Polishing skills, methods or techniques, is essential. Anyone who has ever painted a surface knows that the result is going to be so much better if you pay attention to the preparation. The same principle applies when you are trying to achieve a good electroplated finish. If the metal surface has pits, scratches or other imperfections before you start, unless they are polished out they will still be there in the final finish. That is not to say that the part needs to shine like a diamond before plating, but certainly a good a level of surface preparation and smoothness is required.
Metal polishing is a generic term and includes:
GRINDING – SANDING. Grinding depends on the use of abrasives in any of a number of levels of grit density. Using hand tools or upright lathes, the surface needs to be worked up to a level that will deliver the quality you are looking for. The coarser grit sanding belts, compounds or wheels are used to grind out the deeper imperfections. The metal polisher then uses finer and finer grit densities on the surface until the surface reaches the desired smoothness required.
LINISHING. This is a form of grinding or sanding wherein an upright lathe – often a large machine of several horsepower – with a fitted sanding belt is used. Linishing is a highly skilled operation and should only be performed by an operator experienced in the techniques and safety care required.
POLISHING OR BUFFING. In this step, a softer polishing ‘mop’ or wheel is used, in conjunction with a selection of polishing pastes or compounds, to bring up the surface shine. If NO electroplating is to be done on the item, the polishing or buffing would be the final step in the process of bringing that metal to a nice shine.
VIBRATORY POLISHING. This type of polishing is less reliant on skills and labour and involves placing the parts for polishing into a drum or vessel which contains polishing ‘media’ – usually small stone-like pieces of varying grittiness. The job and media are tumbled or shaken in the vessel, causing vibration to disperse through the media, slowly grinding and polishing the surface. The vibratory process is generally only used for higher volumes of similar parts that require similar treatment. Vibratory polishing is not usually thought of as a good method for achieving very high quality or mirror-like finishes.
Other preparation is also important before plating a metal item. Processes such as cleaning and chemical or electric stripping may also be required and, of course, also need to be managed well if a good quality plating outcome is desired. Please consult A Class if you require any further information about metal polishing and other electroplating pre-treatments.
A Class Metal Finishers provide electroplating, metal polishing and other surface treatment or coating services to manufacturers, restorers and the general public.