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!

Recommended Default Sheet Metal Tolerances

DIM	Tolerance (MM)	Tolerance (Inches)	Description
A	± 0.13	± 0.005	Sheared Edge to Hole
B	± 0.13	± 0.005	2 Holes on One Surface
C	± 0.25	± 0.010	Formed Edge to Hole
D*	± 0.76	± 0.030	Holes Across 2 Bends
E*	± 0.76	± 0.030	Holes Across 4 Bends
F	± 0.25	± 0.010	Sheared Edge to Bend
G	± 0.38	± 0.015	Across 2 Bends
H*	± 0.76	± 0.030	Formed Part

Noted dimensions are to be taken while the part is in a restrained condition. Noted dimensions are for parts within a 12″ envelope.
* Dimensions D, E and H are not recommended forms of dimensioning
These tolerances are recommended and best practices. We can obtain tighter tolerances (depending on part geometry/ construction), contact us for more information Download PDF

Sheet Metal Surface Finish FAQ

What is surface finish, and why is it important in sheet metal fabrication?

Surface finish refers to the texture or smoothness of a metal surface after it has been fabricated. It is essential in sheet metal fabrication because it affects the part’s appearance, performance, and compatibility with additional finishing operations like painting and powder coating.

What are some commonly used surface finish scales for sheet metal fabricated parts?

The Ra (Roughness Average) scale and the grit scale are commonly used to measure the surface finishes of sheet metal fabricated parts. The preferred scale for the source material is also used to specify surface requirements for sheet metal fabricated parts.

How can I achieve the best surface finish for my sheet metal fabricated parts?

To achieve the best surface finish, you should source a material that already has a surface finish comparable to the desired finish. Then, you can use standard methods like employing an abrasive belt finishing machine or using successively finer belts and compounds.

What should I consider before specifying surface finish requirements for my sheet metal fabricated parts?

Before specifying surface finish requirements, you should consider factors like the part’s aesthetic appearance, compatibility with additional finishing operations like painting and powder coating, and cost and time constraints.

How does Approved Sheet Metal ensure that my sheet metal fabricated parts meet my surface finish requirements?

Approved Sheet Metal is committed to delivering sheet metal fabricated parts that meet customers’ specifications and will do what it takes to achieve the desired surface finish. Their attention to detail and quality is second to none, and they offer a quote response ASAP.