The flange face finish is determined by the standard used and measured as an Arithmetical Average Roughness Height (AARH). An example would be ANSI B16.5 which specifies face finishes within a range 125AARH – 500AARH (3.2 Ra to 12.5 Ra).
- Cold Water – It has a mirror like finish. This is made with a wide tool at a high speed which gives a finished surface much like a ground surface. When a surface has this type of finish it is normally used metal to metal, not with a gasket. It is seldom used in the oil, chemical or related industries.
- Concentric Serrated – A 90 degree inclined angle tool is used to make the grove. It makes a grove 1/64″ deep and 1/32″ apart in a concentric circle.
- Smooth – This can be made with several different types of tool shapes. No tool markings will appear to the naked eye on the surface. The roughness of the finish is from 125-250 microinch.
- Spiral Serrated – This is similar to a stock finish but the difference between them is the way the grove is made. A 90 degree inclined angle tool is used to make the grove. It makes a grove 1/64″ deep and the feed is 1/32″.
- Stock – The surface is created by a continuous spiral groove. The roughness of the finish is from 125 to 500 microinches and is cut with a tool with an approximately 0.06 inches or larger radius.