Surface Finish Considerations for Sheet Metal Fabricated Parts (Updated for 2024)

Last updated on January 23rd, 2024 at 12:01 pm

Surface finish is an essential consideration for many sheet metal fabrication projects—including, most commonly, parts requiring beautiful cosmetic appearances and pharmaceutical or medical-grade parts that need to perform in clean environments.

Today, we’ll take a closer look at different surface finishing scales as well as surface finish considerations to ensure you get the exact parts you need.

Surface Finish Scales for Sheet Metal Fabricated Parts

There are several different ways to measure the surface finishes of sheet metal fabricated parts.

Fabricators, machinists, and metal finishers often use the highly technical Ra (Roughness Average) scale, which measures the average surface heights and depths across a surface. The problem is that maintaining a specific Ra value is difficult at a microscopic level for sheet metal fabricated parts—and it isn’t essential for many sheet metal applications.

An alternative method is to indicate the grit—the number of scratches per linear inch of abrasive pad—that should be used to finish a part. Higher grit values indicate smoother surface finishes. This is one of the more common ways that sheet metal fabricators and customers communicate about surface finish requirements.

However, the easiest and best way to specify surface requirements for sheet metal fabricated parts is to use the preferred scale for the source material. For example, we would use this simple scale for stainless steel:

• 2B: Bright, Cold Rolled
• 3: Brushed, 120 Grit
• 4: Brushed, 150 Grit
• 8: Mirror
• BA: Bright Annealed

Creating Beautiful Surface Finishes for Sheet Metal Fabricated Parts

To achieve the best surface finish possible for sheet metal fabricated parts, we recommend sourcing a material that already has a surface finish comparable to the desired finish.Then, we can use one of these standard methods to clean it up even further:

• Employing our Timesaver Abrasive Belt Finishing Machine to clean up the surfaces of sheet metal fabricated parts and get them to spec. This machine is capable of deburring, edge rounding, finishing, laser oxide, and heavy slag removal.
• Using successively finer belts and compounds to achieve a near mirror finish—although this type of finish typically isn’t required for sheet metal fabricated parts.

Surface Finish Considerations for Sheet Metal Fabricated Parts

Consider these factors before specifying surface finish requirements for your sheet metal fabricated parts:

• A higher surface finish doesn’t necessarily result in a better aesthetic appearance. Surface finishes with exceptionally low Ra values lose some of their grain, which can compromise the appearance of the finish in certain cases.

• The smoothest surfaces aren’t always ideal for painting and powder coating. If you plan to have your sheet metal part painted or powder-coated, we recommend leaving some texture on the surface. When the surface is too smooth, these additional finishing operations will highlight any scratches or imperfections. A slightly textured surface yields a more uniform appearance.

• Achieving an exceptionally smooth surface finish adds cost and time to a project. You can save time and money by minimizing surface finish operations on sheet metal fabricated parts. You may consider this option for sheet metal prototypes or internal parts that don’t need to be aesthetically perfect.

At Approved Sheet Metal, we’re committed to delivering sheet metal fabricated parts that meet customers’ specifications and will always do what it takes to achieve the surface finish you desire. Our attention to detail and obsession with quality is second to none. Request a quote today, and we’ll respond ASAP!