How to Install Hex Lag Screws

Lag screws (also known as lag bolts) are some of the toughest fasteners available. They’re used to connect heavy lumber and other materials that will bear intense loads. They differ from normal wood screws, self-drilling screws and sheet metal screws because they require a hole to be predrilled before use, have deeper threading that digs into the material, and include a hex head.

Unlike most screws, hex head lag screws can’t be installed with a screwdriver and must be driven in using a wrench or ratchet. A hex head provides more torque for driving in the screws and helps protect against damage caused by over-tightening.

Most hex lag screws are made from carbon steel, which is exceptionally strong and durable. They’re also available in stainless steel, which offers improved resistance to corrosion in harsh and marine environments.

Hex lag screws are normally coated with zinc for moderate corrosion resistance, hot dipped galvanized for higher durability in outdoor applications, or stainless steel for maximum corrosion resistance. In addition, Portland Bolt manufactures hex lag screws that meet specific ASTM specifications when customers require domestically manufactured products.

When installing hex head lag screws, choose an adjustable wrench that matches the size of the screw and set it loosely around the head. Then, turn the wrench clockwise to tighten or counterclockwise to loosen the screw. If the wrench does not have ratchet action, then it’s best to remove and reset it on the screw several times until you have tightened or loosened the bolt enough.    hex lag screws