A Lag Bolt is a screw that screws directly into wood rather than sliding through a hole and secured with a nut. Lag bolts have as much as nine times more grip in a wood stud than a basic nail and are used to support a lot of weight.
Lag bolts have a thick head that is designed to protrude from the building material. The heads come in a smooth, hammered or classic pyramid square style. They can also be galvanized to provide corrosion resistance. In addition to their high load-carrying capacity, lag bolts are known for their ability to distribute clamping force over a larger surface area and resist compression of the material.
This makes them ideal for use in shear applications. However, lag screws have a tendency to pull out when the head is sheared. Therefore, they should never be used where large forces are pulling directly on the head.
When used correctly, lag screws can provide strong, reliable fastener connections. But it’s important to understand how they differ from other types of fasteners like nails and screws before you choose the best type for your construction project.
The first step in using lag screws is to select the correct size bolt for your project. This can be done by checking your construction drawings and determining the edge distance and end distance of the wood members you’re joining with lag screws. You’ll also need to know what kind of drill bit you’ll need to create the pilot hole and countersink holes for the lag bolt head. A spade drill bit creates these holes and a ratcheting socket wrench is ideal for tightening the lag bolt.