What Is a Small Binding Screw?
A binding head machine screw is characterized by a flat underside of the head, a rounded top, and a trapezoidal cross-sectional shape. They stand out from other round-headed screws such as pan-head and truss screws by having a head diameter that is larger than a pan-head screw but smaller than a truss machine screw.
A machine screw is a screw with a relatively small nominal diameter head, typically featuring slotted or cross-recessed drive parts.
Usage of Small Binding Screws
Small binding screws are designed for fastening objects with internal threads. Unlike other screws, they do not require a tapered counterbore on the fastened object, allowing the screw head to protrude slightly. Due to their large head diameter, small binding screws provide a significant contact area, preventing indentation under surface pressure. They are chosen over truss screws when a smaller head diameter is needed, serving a general purpose similar to pan-head machine screws. Their rounded head also offers an aesthetically pleasing appearance for visible applications.
Common uses include securing parts in home appliances and fastening power cord screws in outlet plugs.
Principle of Small Binding Screws
Small binding screws function by screwing directly into tapped holes, eliminating the need for nuts. Tightening is achieved using a Phillips or flathead screwdriver inserted into the head’s slot or cross-recess. Notably, the length measurement of small binding screws excludes the head height, aligning with the convention for pan head screws and hex bolts, contrasting with countersunk screws where head height is included.
Types of Small Binding Screws
Small binding screws are categorized based on the head’s hole shape and material strength classification:
1. Hole Shape of Machine Screw Head
Head designs include slotted (minus hole) for flathead screwdrivers and cross-recess (plus hole) in H (Philips) or Z (Pozidriv) shapes, each requiring specific tools. The Z type is designed to minimize cam-out during tightening.
2. Material and Strength Classification
Materials include steel, stainless steel, and brass. The choice of material and strength depends on the application’s requirements, with standards ensuring compatibility and performance.
Other Information on Binding Machine Screws
1. Standards for Binding Machine Screws
Specifications are governed by various standards, including ANSI/ASME standards, covering slotted, cross-recessed, and other head types. These standards dictate the screws’ dimensional and mechanical properties, ensuring their suitability for a wide range of applications.
2. Thread Nominal and Length
Nominal sizes range from M2 to M8, with recommended lengths from 3 (4) to 60mm. Specific length ranges depend on the thread size.