AS9120B, ISO 9001:2015, and FAA AC 0056B ACCREDITED

How to Use Sheet Metal Screws

Each major vehicle and machine is dependent on its smallest hardware to be effective. Sheet metal screws are common hardware that are specially designed to fasten sheet metal onto other objects or surfaces made from materials such as metal, plastic, aluminum, plywood, hard rubber, and wood. Many different types of sheet metal screws are available, but in general, most consist of a shank with sharp tips and threads to pierce solid metal and other materials. Due to this capability, they are often used in aircraft construction for fixing the aluminum sheets frequently used in aviation.

Sheet Metal Screw Types

Sheet metal screws can be divided into two major categories based on their method of installation: self-tapping and self-drilling.

Self-tapping Sheet Metal Screws: Self-tapping screws have a sharp point and threading which allows them to twist tightly into piloted or pre-drilled holes. They are able to burrow in a surface and are advantageous for their fast installation, effective corrosion protection, excellent holding power, and variety of head options available.

Self-drilling Sheet Metal Screws: Self-drilling screws have a tip which is more like a drill point in order to penetrate a surface without a pilot hole. As such, they are often specially designed to fit on a drill bit. Some benefits are that they take less preparation time to install, are corrosion resistant, create less mess, and have consistent performance across a variety of materials.

Point Types

  • Type A: These screws have coarse threads and gimlet points and are used to mount thin metals and wood.
  • Type AB: AB point-type screws have fine threading as well as a gimlet point. These screws are ideal for fragile materials because of their thin threads.
  • Type B: These screws have blunt tips and spaced threads for plastic or plywood, as well as thinner metals.

Head types

  • Flat: The Phillips or slotted style head on this type can lay flush to a surface. As such, they are very good for countersunk mounting.
  • Hex: These screws have a hexagonal head that is often used with a nut for a more sturdy fastening solution.
  • Hex Washer: As the name would suggest, these screws have both a hexagonal shaped head and an attached washer. Some may have an external hexagonal shape while internal hex screws have a hexagonal recess in them for attaching a nut in their center.
  • Oval: These screws have a head which protrudes a little from the surface they are driven into. The head is domed for lesser wind resistance and a smoother finish.
  • Pan: Pan head screws are also rounded and protrude above a surface; however, their shape is more like a smooth flat disc than a half-sphere.
  • Truss: Truss head screws have a wider head and a rounded top with a Phillips-style slot.

Slot Type

  • Cross: Also known as a double-slot, cross-slit screws have two slots which are perpendicular to each other. They can be fastened using a slotted or Phillips screwdriver.
  • Slotted: The original slot type, these screws have just one slit down the center of the screw head. A flathead screwdriver can be used to tighten them.
  • Square: Square slotted screws are recessed so they don't slip when being tightened.
  • Combi: Combination or just “combi” screws have slots which resemble all three slot types, so they can be fastened by several different screwdrivers.


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