Industrial Grade Through Bolts Expansion Wedge Anchor Bolts for Concrete

Through bolts are a type of mechanical fastener designed to clamp materials together by passing completely through all the layers being joined. They consist of a threaded bolt and a nut that is tightened on the opposite end from the bolt head. Unlike screws which grip into a material, or bolts that thread into a blind hole, through bolts create a strong, reliable connection by compressing the materials between the bolt head and the nut. This design allows for high clamping forces and is commonly used when joining thick materials or when a detachable joint is required.

Materials

Through bolts are manufactured from a variety of materials, each selected for specific strength and environmental properties:

• Carbon Steel: The most common and cost-effective material, offering high strength for general construction and industrial use.
• Stainless Steel: Provides excellent corrosion resistance, making it ideal for outdoor, marine, and food processing applications. Common grades include 304 and 316.
• Alloy Steel: Often heat-treated for high-stress applications requiring superior tensile strength, such as in heavy machinery and structural steel connections.
• Galvanized Steel: Carbon steel coated with a layer of zinc for moderate corrosion protection, frequently used in outdoor construction.
• Brass: Offers good corrosion resistance and electrical conductivity, often used in plumbing and electrical applications.

Surface Finishes

The surface finish is applied to enhance durability, corrosion resistance, and sometimes appearance:

• Plain (Black): No coating; used in indoor, dry environments.
• Zinc Plated: A common, economical finish that provides a basic level of corrosion resistance for indoor and light outdoor use.
• Hot-Dip Galvanized: A thick, durable zinc coating applied by dipping the bolt into molten zinc. This is standard for heavy outdoor and marine construction.
• Mechanical Galvanized: A zinc coating applied without heat, used to prevent hydrogen embrittlement in high-strength bolts.
• Passivated: A chemical treatment for stainless steel to remove free iron and enhance its natural corrosion-resistant oxide layer.

Specifications

Through bolts are defined by several key specifications:

• Diameter: The nominal thickness of the bolt shaft (e.g., 1/4 inch, 1/2 inch, M10, M20).
• Length: Measured from under the head to the end of the bolt, chosen to accommodate the thickness of the materials plus the nut and washer.
• Thread Pitch: The distance between threads (coarse or fine), which affects holding power and installation speed.
• Grade / Class: Indicates the bolt’s tensile strength (e.g., SAE Grade 2, 5, 8 or ISO Property Class 4.6, 8.8, 10.9).
• Head Type: The shape of the head (e.g., Hex, Square, Socket Cap) which determines the tool needed for installation.

Applications

The versatility of through bolts makes them essential across numerous industries:

• Construction: Steel beam connections, securing wooden posts to concrete foundations, and heavy timber framing.
• Infrastructure: Bridge building, highway sign supports, and railway track assembly.
• Industrial Machinery: Assembling heavy equipment, conveyor systems, and motor mounts.
• Automotive: Leaf spring shackles, engine mounts, and chassis components.
• DIY/Furniture: Assembling flat-pack furniture (with barrel nuts), creating sturdy shelving units, and repairing tools.

Excellent Case

A homeowner needed to hang a heavy 50-pound swing set from a large wooden beam in their backyard. Using lag screws risked splitting the wood, so for safety and durability, they used two 1/2-inch galvanized through bolts. They drilled holes completely through the beam and bracket, inserted the bolts with large washers, and tightened the nuts. The through bolts created a strong, weather-resistant connection that safely supports the swing’s dynamic load year after year.