There are four major types of surface finishes that are designated for stainless steel. While many of these finishes are somewhat subjective, below is a guideline for the most common finishes:
#3 Coarse Finish — Usually a preliminary, coarse surface finish. Also referred to as rough grinding. Used for removing gates from cast parts, heavy burrs, weld splatter. Often accomplished with a disc or belt grinder but parts can be tumbled part-on-part with an abrasive grit to achieve a #3 finish.
#4 Brushed Finish — Defined as a directional or uniform surface finish. Removes surface defects in the surface but accepts fine polishing lines. A #4 Sanitary Finish is a slightly smoother, polished finish commonly designated in the food, dairy and medical industries. Tumble polishing can be used to accomplish a close approximation to a #4 Finish.
#6 Fine Finish — A polished, softer version of a #4 Finish. Often less reflective than a #4 Finish. No polishing lines or surface defects visible.
#8 Polished Finish — All surface defect are removed. Mirror-like finish depending on the quality of the metal. Highly buffed surface.