Also called Grinding, Roughing or Rough Grinding. These finishes are coarse in nature and usually are a preliminary finish applied before manufacturing. An example would be derburring or removing excess weld material. It is coarse in appearance and applied by using 36-100 grit abrasives. When the finish is specified as #3, the material is polished to a uniformed 60-80 grit.
Also called brushed, directional or SATIN finish. A #4 architectural finish is characterized by fine polishing grit lines that are uniform and directional in appearance. It is produced by polishing the metal with a 120-180 grit belt or wheel finish and then softened with an 80-120 grit greaseless compound or a medium non woven abrasive belt or pad.
This finish is commonly used for the medical and food industry - almost exclusively used on stainless steel. This finish is much "finer" than a #4 architectural finish. Great care should be taken in removing the surface defects in the metal - like pits - that could allow bacteria to grow. A #5 Diary or Sanitary finish is produced by polishing with a 180-240 grit belt or wheel finish softened with 120-240 grit greaseless compound or a fine non woven abrasive belt or pad.
This finish is produced by polishing with a 220-280 grit belt or wheel softened with a 220-240 greaseless compound or very fine non woven abrasive belt or pad. Polishing lines should be soft and less reflective than a #4 Architectural Finish.
A #7 Finish is produced by polishing with a 280-320 belt or wheel and sisal buffing with a cut and color compound. This is a semi-bright finish that will still have some polishing lines but they should be very dull. Carbon steel and iron are commonly polished to a #7 finish before chrome plating. #7 finish can be made bright by color buffing with a coloring compound and a cotton buff.
This finish is produced by polishing with at least a 320-400 Grit belt or wheel finish. The part is sisal buffed and then color buffed to achieve a mirror finish. The quality of this finish is dependent on the quality of the metal being polished. Some alloys of steel and aluminum cannot be brought to a mirror finish. Castings that have slag or pits will also be difficult - if not impossible - to polish to a #8.