Mechanical Finish Designations

A Guide to Mechanical Finish Designations

#3 Finish 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 deburring or removing excess weld material. It is coarse in appearance and applied by using 36-100 grit abrasive. When the finish is specified as #3, the material is polished to a uniform 60 - 80 grit.

#4 Architectural Finish 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.

#5 Dairy or Sanitary Finish 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 #4 Dairy 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.

#6 Finish or Fine Satin FinishThis finish is produced by polishing with a 220 - 280 grit belt or wheel softened with a 220 - 230 greaseless compound or very fine non woven abrasive belt or pad.

#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. A #7 finish can be made bright by color buffing with coloring compound and a cotton buff.

#8 Finish or Mirror Finish This finish is produced by polishing with at least a 320 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.