Lag screw sizes are determined by the size of the head and thread. As with any screw-in fastener, ensuring the proper size of the lag bolt is important to the success of your project. If you have a lag screw that is too big, the load-carrying capacity of the structure will be diminished. Conversely, a lag screw that is too small will not be able to bind to the materials and may fail during installation.
Lag bolts differ from normal wood screws in that they do not thread as the screw enters the material but rather create a helical structure around the body of the screw. For this reason, they require a drilled hole to be installed correctly. The lag screw’s hex or square-shaped head is also larger than a typical wood screw.
In addition to a hex wrench or ratchet, a tape measure is needed for measuring the length of a lag screw’s threads and determining the correct size. Clamps are also necessary to hold the materials together during the drilling process.
Unlike wood screws, which may be used in any species of sawn lumber, hex lag screws are only available in a limited number of head types and sizes. Portland Bolt manufactures hex lag screws in the most common ASTM specifications and can customize the head dimensions or material to meet specific project requirements.
Hex lag screws are usually available in stainless steel, carbon or hot dip galvanized to resist corrosion in harsh environments. It is recommended that the holes into which hex lag screws are installed be saturated with a preservative to protect against decay fungi (refer to American Wood Protection Association Standard M4: Standard for the Care of Preservative-Treated Lumber). Beeswax or paraffin wax can be used to lubricate hex lag screws during installation, although bar soap is an acceptable alternative. Lag screw sizes