Fasteners are hardware devices that mechanically join or attach two or more objects. They include removable items like screws, bolts, nuts, and rivets, as well as permanent joining processes like welding and brazing.
What’s Fastener
Fasteners can provide either a permanent or non-permanent connection between parts.
- Permanent fasteners like welds and structural adhesives cannot be undone without damaging the pieces.
- Non-permanent fasteners like screws and nuts allow for easier disassembly.
Regardless of the type, fasteners are essential in any manufacturing process. They hold together everything from small electrical components to entire vehicles and structures. Without reliable fastening systems, manufacturing assemblies would not function properly or last long in the field. Therefore, proper fastener selection and installation are crucial for maximized production uptime and quality control.
Fastener Basics
To select and install fasteners correctly, it’s important to understand some basic characteristics and terminology. Whether permanent or removable, all fasteners generally have common elements that define their function and suitability for different applications.
Types of Common Fasteners
There are two main categories of fasteners:
Threaded Fasteners
Threaded fasteners like nuts, bolts, and screws use helical external and internal threads to bind and tighten parts together. The torque applied when twisting them into place creates a clamping force to resist loosening, allowing adjustable installation and disassembly. Different thread shapes affect strength and ease of use. They come in metric and imperial sizing with coarse or fine spacing.
Non-threaded fasteners
These fasteners join through mechanical deformation rather than threads. Non-threaded fasteners provide more permanent solutions. An example is Rivets, which have a tubular shape with ends mechanically deformed during installation to flare out and grip both sides of a joint. Other non-threaded fasteners are retaining rings and circlip. They snap into machined grooves to hold components like bearings and cylinders securely. More non-threaded options include pins, springs, and adhesives.
Fastener Materials
The material used to construct fasteners heavily influences strength, corrosion resistance, temperature thresholds, magnetic qualities, weight, and cost.
Steel
Low- and high-carbon steel offers high tensile strength and hardness for load-bearing applications but can rust without protective plating or coating. Common grades include SAE J429 Grade 5 and hardened SAE J429 Grade 8. Stainless steel provides corrosion resistance in harsh environments.
Stainless Steel
With added chromium and other alloys, stainless steel resists corrosion and staining much better while maintaining high strength. Grade 303 is a good balance of price and performance. More expensive grades like 316 are suitable for severe chemical exposures.
Aluminum
Aluminum provides lightweight, corrosion resistance, and conductivity at a lower cost but has less shear and tensile strength than steel options. Grades differ in hardness, weldability, and machining properties. Series 6000 aluminum alloys pair well with steel and itself. Core advantages are strength and corrosion properties superior to plain steel.
Plastic
Engineered thermoplastics offer cost-effective, lightweight options. Nylon is self-lubricating and withstands moderate heat and impacts. PEEK resists chemicals and temperatures up to 500°F while maintaining strength.
Additionally, brass and silicone bronze are used for fasteners in select applications where resistance to corrosion, chemicals, heat, or electricity matters more than high strength. The material you will select ultimately depends on factors like budget, strength demands, and environmental conditions the fastener must endure.
Fastener Strength Grades
The material alone does not determine a fastener’s strength. Manufacturers further classify fasteners by their minimum tensile strength ratings. These grades indicate the torque or axial load a fastener can withstand. The special markings on screw heads and nuts can help you identify the fastener’s grade. A head with no markings is Grade 2, 3 lines spaced 120 degrees is Grade 5, and 6 lines spaced at 60-degree intervals is Grade 8.
Mor discussion please feel free contact us.
Author: paoyue