Lag Screws: What They Are and How to Use Them

Also commonly known as lag bolts, lag screws are some of the toughest fasteners. These extremely sturdy fasteners are usually used to connect heavy lumber or other heavy materials that are bearing an intense load.

These screws differ from normal wood, self-drilling or sheet metal screws. Compared to most ordinary screws, lag screws are massive in size. Most lag screws are at least one inch long and ¼-inch thick.

For example, wood screws are used when connecting an application with only wood materials. These wood screws boast coarse threading, but that threading does not encompass the length of the screw. Normal wood screws thread as they enter the wood, where lag screws require a hole to be drilled first. Lag screws also use a nut to add extra strength and security to help hold things together. Used for intense load applications, lag screws can support a much heavier load than the average sheet metal or wood screw.

To install lag screws, the first step is to make sure that all of the materials involved in the application are aligned. To keep the materials in place once they are aligned, use clamps to hold. Once everything is secure, drill a pilot hole using a bit with a slightly smaller diameter than the lag screw that will be used. When drilling the hole, make sure to drill all the way through the area where the screw will eventually be.

Lag screws are also only available with hex heads while more common wood and sheet metal screws are available in multiple head types. With the sole option of a hex head, installation of the screw will require a nut driver or ratchet. A right driver bit and a power drill can be used to finish the tightening of the lag screw. The hex head lag screw is designed that way since hex headed fasteners are made to hold up in applications where a lot of torque is necessary. Lag screws have sharp lead thread points and are available in Steel/Zinc, Stainless Steel, and Steel/Hot Dip Galvanized.

For more information about lag screws, their uses, or how to install them, contact us at ProvenProductivity@bossard.com.

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