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What is Lag Bolts

A lag bolt, or lag screw, is a type of fastener used for making mechanical connections between two pieces of wood to ensure that they are held together securely. These bolts are often used to fasten large beams and posts used for decking, wooden bridges, and other wooden structures. They can also be used in concrete, but require a special insert, called a lag.

These fasteners are directly screwed into wood. They have a large head on one end and a cylindrical shaft with smooth and externally threaded parts along its length. The smooth section of the length is located directly below the head. The threaded portion contains a helical structure that allows the screw to be advanced and tightened when rotated clockwise. The thread tapers to a sharp point at its end to help engage the screw by embedding into the surface of the wood.

Lag bolts are tightened and loosened by applying torque to the head of the bolt using a tool. The head of the bolt is larger than the threaded portion to provide a positive mechanical stop and to allow a tool to be used when tightening. It also has a hexagonal shape for use with an open-end or box wrench, or ratchet.

Lag Bolts

Lag bolts are often referred to as lag screws. Lag bolts are not like other bolts. They look like a screw rather than a bolt with their pointed end instead of the more common blunt end found on most bolts.

Lag bolts or lag screws may be made out of steel, stainless steel, or silicon bronze, and can be hot-dip galvanized to accommodate any and all projects as needed. Mostly used in the construction field, lag bolts are also commonly used for a variety of projects in and out of the home. 

Lag bolts are made from a variety of materials to accommodate the abundance of applications in which lag bolts are used. Below are some of the more common styles of lag bolts and lag screws. 

Common Types of Lag Bolts / Screws

  • Zinc-plated lag bolts/lag screws: Moderate protection against rust.
  • Stainless steel 18-8 lag bolts/lag screws: With high corrosion resistance, stainless steel is the material of choice for lag bolts in exterior and marine applications.
  • Silicone bronze lag bolts/lag screws: Used in wood boat building this alloy of copper has better strength and corrosion resistance than brass.
  • Hot dipped galvanized lag bolts/lag screws: Much more corrosion resistant than zinc-plated. These thick coated lag bolts with galvanized butts are ideal for exterior use in coastal areas.

Other bolt/screw types available

• Anchor bolts - extended connections with handle
• Carriage bolts - domed top with square under head
• Flange bolts - ridge around the bolt head
• Hex bolts - hex head of various materials
• Hex tap bolts - trimmed hex head with no flange
• Machine bolts - fine or coarse threads
• Metric bolts - available in Hex/Standard/Flange type
• Shoulder bolts - allow slide or pivot
• Square neck bolts - square or domed top with square under head

Types of Bolts


Lag Bolts Application Industries

Sunflex Metal Industries are engaged in manufacturing of robust quality of Lag Bolts. These Lag Bolts are widely used in the following industries:

Lag Bolts Mining Industries
Lag Bolts Transport Industries- Rail and Road
Lag Bolts Construction Industries / Building Systems
Lag Bolts Manufacturing Industries
Lag Bolts Agriculture Industries
Lag Bolts Energy Industries
Lag Bolts Water Industries
Lag Bolts Automotive Industries
Lag Bolts Ship Building Industries
Lag Bolts Nuclear Power Plant
Lag Bolts Paper & Pulp Industries
Lag Bolts Sugar Industries
Lag Bolts Engineering Cement Industries
Lag Bolts Petro-Chemical Industries
Lag Bolts Food Industries
Lag Bolts Oil & Gas Industries
Lag Bolts Chemical & Pharmaceutical Industries

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