Lag Bolt Pilot Hole Size
Unlike standard screws that cut their own holes as they are screwed in, lag bolts must have a pilot hole made for them. Having the correct pilot hole will help ensure the screws are inserted and driven in correctly and can be tightened without snapping the head of the screw off.
Lag bolts are threaded metal fasteners that are commonly used to connect wood together, primarily studs to joists. They can also be used in metal by drilling a hole the appropriate size and driving them in with a socket wrench. The lag bolt’s large head, cylindrical shaft, and externally threaded parts all help provide the strength needed for these types of applications.
Using a pilot hole for lag screws is important to avoid splitting or damaging the wood in which they are installed. It is also important that the lag bolts penetrate at least twice their own major diameter into the material that they are being secured to. Driving them any deeper than this runs the risk of them breaking off in the material or not providing a sufficient hold.
To pre drill a hole for a lag screw, use a bit that is the same size as the root diameter of the unthreaded section of the bolt. This diameter can usually be found printed on the head of the bolt. It is recommended that a bit slightly smaller than this be used, as it will make it easier to install the lag bolts. Once the hole is drilled, it should be lubricated with either beeswax or paraffin wax to prevent it from loosening over time. Bar soap is sometimes suggested, but this can accelerate the rate at which the lag bolts rust as it contains glycerin. pilot hole for 3/8 lag screw