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Understanding Sheet Metal Finishes in sheet metal fabrication: Quality and Cost


There is not a unified approach for the classification of finishes for sheet metal parts. An easy approach in terms of quality can be "first class, second class, and third class". (Dependent on your country of residence, the finish classification naming can be different; Nevertheless, the general principles still apply everywhere).

The first class or "cosmetic finish" is the best, finest finish and it is free of any surface imperfections or press brake marks, and it is typically reserved for external parts requiring delicate finish, such as for medical or food processing needs/uses. Parts that will be anodized also require a first-class finish.

To achieve such a light grain finish a sanding, grinding, or polishing machine, or a stroke sander can be used to remove all surface imperfections.

The second class, or the "standard" finish class, is not considered cosmetic, and is a more economical option, so some surface imperfections can be expect, including press brake marks. Parts that are plated typically fall into this class.

The so called second-class finishes can be further classified according to the respective processes:
• Machine finish (polishing, grinding, or sanding): The finish appearance is of linear light grain.
• Manual finish (sand). The finish appearance is nonlinear (circular or ‘orbital’).
• Tumble finish: obtained by placing small metal parts in a tumble machine. The finish appearance is smooth, non-linear.

The default finish at most sheet metal fabrication shops ("mill finish") is also known as the third class.

Parts with a third-class finish are smooth enough to not be harmful, with no significant burrs, but there will be some surface imperfections, such as press brake marks. No sanding, grinding, and polishing machine employed; this is the shop standard for parts to be painted.
    Portoroz, Primorska - si

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