Notches and tabs are two of the most common features found in precision sheet metal parts, and it’s easy to see why. Adding these features gives you space to get tools into an area. Also, they help avoid space conflicts between parts or features, especially when incorporating parts together in an assembly.
Why Should I Use Notches and Tabs?
These features can be useful for locating parts in an assembly, much like slots can. A tab on an interior part simply slides into a notch on a chassis or box. Doing that can help more precisely locate the part before riveting, or even welding, in places where location and strength are more important than aesthetics.
Dimensional Rules for Notches
As with all good things in manufacturing, there are rules designers must follow and that applies to adding tabs and notches, too. Notches should follow one of these two criteria. Width should be at least .040 in. or the material thickness, whichever is greater. Notch depth should be no deeper than 5x its width, depending on its purpose.
Dimensional Rules for Tabs
Tabs should be at least the material thickness in length and 2x the material thickness in width, not going more than 5x in width. Although there are exceptions to these guidelines, if you can maintain these basic dimensions, you’re ensuring strong tabs and structurally sound notches.
Strategies for Limited Space in Sheet Metal Assemblies
More and more, assemblies are shrinking in size, the need to notch flanges near screws, nuts, or electronics has become almost inevitable. Still, it’s important to balance the need for space with the structural strength of the part. Following the basic criteria listed above as much as possible will ensure strength and structural integrity.
In some situations, you can use bent tabs in tandem with spot welding or riveting to place a part without the need for a longer flange or fillet welding. These bent tabs would still need to follow the general rule that the tab’s length should be at least 4x material thickness in length.
For more helpful sheet metal design tips, download our Design for Manufacturing (DFM) Guide.