Tech Tip: Installing Lag Screws

Lag screws are made of unhardened steel (or stainless steel, which is also unhardened, but is stronger than the mild steel used in standard lags). That means that lag bolts are soft, and can easily be over-torqued and broken during installation. Worse yet, if such a thing is possible, is that many users mistakenly think that because of their size compared to standard screws, lag screws do not need pilot holes. Unfortunately, the wedging action of a large-diameter lag screw will quickly split most lumber! For best results, drill a pilot hole for the threads, and a clearance hole for the shank. I generally drill the pilot hole through both pieces at one time for alignment, then enlarge the pilot hole to the clearance hole size in the piece being fastened .