Unlike standard screws, which can be screwed directly into wood, lag bolts require a pilot hole. The proper size of the pilot hole will help ensure a strong and lasting connection, as well as prevent damage to the materials being fastened.
Generally speaking, the pilot hole should be as long as the body of the lag bolt, but no longer than the threaded portion. For this reason, it’s recommended that a twist drill bit be marked with tape at the proper depth for the unthreaded portion of the shank (NOT including the point).
The diameter of the pilot hole should match the bolt’s root diameter. Variables such as wood type and bolt length also affect ideal pilot hole sizes. A common mistake is drilling a hole too large, which will cause the lag bolt to over-penetrate and compromise withdrawal resistance.
Lag bolts are designed to fasten two pieces of material together, such as studs or plates, without weakening them. They are the strongest of all screw types, and when installed properly, will create a strong, permanent connection.
To maximize their holding power, lag bolts should be driven into the surface by at least two inches. This ensures that they will not be pulled out or broken when the material is subjected to a significant amount of stress. It’s also important to lubricate the lag bolt with beeswax or paraffin oil during installation to avoid friction between the bolt and the materials it’s being fastened to. pilot hole for 1/4 lag screw