What Is a Small Truss Head Screw?
A small truss head screw features a flat screw head with a rounded top, offering a larger diameter than small pan head screws and a lower profile than small binding head screws. For visual reference, see Figure 1 depicting truss head screws alongside pan and binding head screws.
Figure 1. Truss Head Screw, Pan Head Screw, Binding Head Screw
“Small screws” are defined as having a relatively small nominal diameter, typically with slotted or cross-shaped driving parts.
Uses of Small Truss Head Screws
Small truss head screws are commonly used in applications where the female thread is directly created in the item being fastened, such as in door knob and guard installations, as illustrated in Figure 2.
Figure 2. Example of Using Truss Head Screws
These screws offer a large head diameter for increased contact area, enhancing resistance to loosening. The rounded head also contributes to aesthetics and prevents the seat surface from sinking into fastened parts, making them ideal for wooden components.
Principle of Small Truss Head Screws
Small truss head screws are designed for direct fastening into tapped holes without the need for a nut, tightened using Phillips or flat-blade screwdrivers. The length of these screws is measured excluding the head height, a distinction important for accurate application.
Types of Small Truss Head Screws
The classification of small truss head screws can be based on the head hole shape or material strength, as detailed below and in Figure 3.
Figure 3. Types, Materials, and Shapes of Truss Head Screws
1. Classification by Hole Shape of the Screw Head
Small truss head screws feature either a cross (Phillips or Pozidriv) or slotted head design, each requiring specific tools for tightening.
Figure 4. Truss Head Screw Head Hole and Tool Shape
2. Material (Strength Classification)
Materials range from steel and stainless steel to nonferrous metals, each classified by strength and adhering to specific standards.
Other Information on Small Truss Head Screws
Standards such as ANSI/ASME B18.6.3 govern the specifications for small truss head screws. Sizes typically range from M2 to M8, with recommended lengths from 4 to 60 mm.