Slots and Tabs - VTAstrobotics/Documentation GitHub Wiki

Slots and Tabs

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The slot and tab joint is a method used in assembling sheet metal parts. It involves two perpendicular metal plates, one with a slot and the other with a tab that fits into the slot. This type of joint is relevant for its use in ensuring efficient assembly, consistency, and structural integrity in metalwork.

Description

  • Slot: A rectangular cut into one part to accept the tab from another part.
  • Tab: Protrudes from one part to fit into the slot of another part.

Purpose

Slot and tab joints are utilized:

  • To improve assembly efficiency by reducing alignment issues.
  • To ensure consistent positioning between components.
  • As reference points for measurements on fabrication drawings.

Considerations

When designing or using slot and tab joints:

  • The fit should not be too tight to avoid stress concentration.
  • Adjustments may be necessary based on material thickness or desired tolerances.
  • Slot and tab should not be used alone for structural stability but rather as an aid to other fastening methods such as welding or riveting.
  • Over-reliance on slots and tabs can lead to reduced strength if not properly designed or implemented.

Sizing

The slot length and width must always be slightly larger than the tab, but the amount of clearance needed varies based on material thickness. Thinner parts can be designed with a tighter fit due to the higher precision from the laser and reduced kerf effects along the edges.

For example, if both parts are less than 3/8” thick, a β€˜nominal’ clearance of 0.004”-0.005” can be used around all sides of the tab. If one or both parts are 3/8” thick or greater, a nominal clearance of 0.008”-0.010” can be used. Keeping a tight fit across the slot/tab width while letting the length fit more loosely is often beneficial.

Many applications of slot and tab design use the nominal (tight) clearance for the slot width since the tab width (plate thickness) is tightly controlled and not laser cut. Conversely, a more generous clearance (e.g., 2x the nominal clearance, or more) is often used for the slot length to aid in assembly.

Regarding tab depth, most applications where the slot will be plug welded use a tab depth between 1/2 to 2/3 of the slot depth. For instances where the slot is not plug welded it is recommend having the tab extend to be flush with the opposite side of the slot. Note that rust bleed is very likely on painted parts where the slot/tab is not plug welded. With very thin materials (< 0.10”) it may be necessary to use full- depth tabs for ease of assembly, even when the slot will be plug welded subsequently.

In general, a single slot and tab feature should be no longer than 2” to avoid excessive plug weld length.

Slot and Tab Quantity

Using multiple slot/tab features along the edge of a part is preferred. A single, overly long slot/tab should not be used in place of multiple slot/tab features. Some manufacturing divisions require at least two (2) slot/tab features along each edge, and three (3) if the edge is >24” long.

Slot and Tab Corners

The consensus among most manufacturing-controlled documents is that no fillets should be used in the corners of the slot, nor the internal corners of the tab. The external corners of the tab may have fillets.

Other Considerations

  • Slots and tabs should be avoided in areas of high stress or cyclic loading.
  • Slot and tab features can create additional rust points between raw steel surfaces when full welds on both sides of the slot are not specified, paint coverage inside the slot and tab joint should be considered minimal.
  • Some divisions have noted that slot and tab features are not advised on parts β‰₯ 3/4” thick.