What Is a Lag Screw?

Lag screws (also known as lag bolts) are larger and stronger than wood screws. They are used to hold heavy loads and require pre-drilling.

Ellis28 reported that lag screw fixation of mandibular body and symphysis fractures is simple, rigid, and allows function with a minimal risk of complications. It is also cost-effective.
Types

Lag screws are heavy-duty fasteners used to connect lumber and other materials that bear a significant load. They differ from wood screws, self-drilling screws and sheet metal screws in that they use a hex head and require a special socket wrench for installation.

Hex lag screws have a hex head, which makes them easier to drive into wood than traditional screws with recessed heads. They also can withstand much more force than traditional screws because of their thicker shafts.

While hex lag screws are easy to drive, they’re not the easiest for wood-to-wood connections because they do not require a pilot hole. Luckily, they are ideal for most other applications where a conventional screw can’t hold up to the weight of the application. They’re typically a better choice than carriage bolts, which require pre-drilled holes and can displace wood fibers when driving them in.
Materials

Unlike wood screws that can easily break or lose their grip, lag bolts are made of materials that can stand up to significant pressure. They have a high shear strength that makes them ideal for projects like pole line utilities, deck framing and outdoor play equipment.

Because of their superior load bearing capacity, lag bolts can also be used to fasten metal and concrete components together. Those that will be exposed to the elements can also be galvanized to resist corrosion.

Lag screws are also useful for transgingival closure of the alveolar process fracture (TPF). In a recent experimental study, Ngassapa et al found that lag screw osteosynthesis was less traumatic than the Merkx prefabricated arch bar splint and resulted in improved oral hygiene with minimal plaque retention around the screw. They also reported that the TPF was stable with no bone resorption in the fractured area. The screw was also easy to insert through the gingiva without disturbing the compromised blood supply to the broken fragment.
Applications

Lag screws are commonly used to fasten lumber or other heavy materials that must withstand a strenuous load. They are longer and thicker than other types of screw, which helps to make them more robust.

They can be used in a variety of applications, including securing metal and wood to stone, concrete or other hard surfaces. They can also be used as a substitute for nails in some cases.

These tough screws are also useful for fastening items to a wooden surface that may be subjected to vibrations or jolts. While other fasteners such as carriage bolts can be used for this purpose, lag screws offer more durability and a greater shear strength.

These heavy-duty fasteners can be installed with a drill or ratchet, and they can be tapped into place using a hammer. Before installation, you should ensure that the materials are properly aligned. You should also pre-drill a pilot hole in the material into which you intend to drive your lag screw.
Installation

Unlike wood screws or machine screws, lag bolts do not require a nut on the opposite side. Instead, their holding power comes from friction between the threads and the wood fibers themselves.

They are one of the toughest construction fasteners around, used to connect lumber or materials that will bear a strenuous load. In fact, they are monstrous in comparison to standard screws like wood or sheet metal screws, which have a much thinner thread and screw into precise matching holes drilled and tapped into the material.

Prior to use, a pilot hole needs to be drilled through the material you will fasten the lag screw into. The diameter of this hole should be slightly smaller than the size of your lag screw. To do this, clamp together the two materials to be fastened and mark a location for the drill bit. Then, drill through both materials with a bit that is proportionally sized to the lag screw you plan on using.