Lag Bolt Pilot Hole Size
If you’ve been a contractor for any length of time or have undertaken a major construction project, you are probably very familiar with the use of lag bolts. These heavy-duty fasteners, also known as lag screws, are much stronger than standard screws and have a larger diameter shank that allows them to dig deeper into the material they’re being used in. They can also withstand high tensile and shear forces. The ideal lag screw pilot hole size is determined by the wood type, bolt length and diameter, and other environmental factors.

Lag bolts are usually installed so that the threaded portion of the bolt is embedded by a minimum of five times its diameter. This is to help ensure that the lag bolt has the necessary strength to securely hold your material together. If you’re not sure what size of lag screw to choose for your application, consult an engineer or review local building codes for guidance.

Unlike most screws, lag bolts require pre-drilling before installing. This is because of their large diameter, and if you drive them in without first making a pilot hole they will likely split the stud, which can lead to weakened structures.

Creating the proper pilot hole for a lag screw is easy with the right drill bit. First, align your drill bit horizontally with the lag screw and make sure the holes match each other. If the holes are not exactly the same, start with the largest drill bit and then work your way to the smallest until you have found the correct drill size. pilot hole for 3/8 lag screw