Stainless steel bar polishing is an important process for manufactures and architectural applications. Polishing stainless steel bars creates a uniform and consistent surface finish–vital for tank manufactures and OEMs supplying products to the chemical and pharmaceutical industries. Penn Stainless inventories polished bar in #4 polish, #6 Polish, #7 polish or a #8 mirror finish. This section provides information on different stainless steel finishes, technical data, and best practices for ordering material. Check back fore more updates. We are just getting started with this section of our website. Contact us with any questions you have!
The stainless steel is cold rolled, softened and descaled, similar to the process of a 2D finish. It then receives a final light pass on polished rolls known as a ‘pinch pass’. The steel remains gray in appearance, but the final pass on polished rolls produces a smoother, brighter surface than 2D finish. This is a general purpose, cold rolled finish; it is suitable for a wide range of stainless steel applications and wide range of subsequent polishing processes, such as satin finishing. Typical uses for 2B finish include non-decorative or functional sheet metal products, industrial refrigeration equipment, chemical plant and plumbing fixtures.
No. 4 Finish is produced with short, parallel polishing lines. These lines extend uniformly along the length of the coil. It is obtained by mechanically polishing a No. 3 finish with gradually finer abrasives. Depending on requirements, the final finish can be between 120 to 320 grit. High grit numbers create finer polishing lines and more reflective finishes. The surface roughness is typically Ra 25 micro-inches or less. This is a general-purpose finish, and is widely used for kitchen/restaurant equipment, food processing, and dairy equipment.
No. 6 Finish is a dull, silver white finish with relatively short linear polishing lines.The No. 6 finish has a lower reflectivity than No. 4 finish, and is produced by Tampico brushing aNo. 4 finish sheet in an oil and abrasive medium. This finish often used for stainless steel architectural projects between the 1930 – 1980’s. It is no longer produced by toll polishing houses, but custom fabricators sometimes apply it to small projects.
No. 7 Finish is very reflective and has a mirror-like appearance. A No. 4 finish that has been polished to 320-grit is buffed for up to 10 minutes but existing grit lines are not removed. Fine polishing lines can often be seen by an observer standing several feet from a panel.This finish is often used for ornamental purposes, such as trim, column covers, or wall panels.
No. 8 Finish is the most reflective finish covered by ASTM standards. It is produced using the same process as No. 7 finish except that buffing continues for an additional five to ten minutes. The grit lines are much less visible than the No. 7 finish, but can still be seen if examined closely. The resulting finish is the closest finish to an actual mirror, but is not perfectly reflective.
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