Insert a 1/2-inch Forstner bit into the drill/driver and drill into the hole to a depth of 1/2 inch. This is the countersink hole to hide the head of the bolt. Insert a 3/16-inch bit into the drill/driver for softwood. Insert a 7/32-inch bit for hardwood.Click to see full answer. Moreover, how long should a lag screw be?You will usually need to pre-drill a 5/16” pilot hole into the rim joist if you are using ½” lag bolts. Your bolts or screws should be long enough to extend at least ½” past the board you are attaching to. They are usually installed in a zig-zag pattern.Also Know, how do you screw a lag bolt into wood? To install a lag screw, first you have to align the materials you’re going to screw together. When they’re lined up, clamp them together so they stay in place. Then, using a bit with a slightly smaller diameter than your lag screw, drill a hole all the way through the materials where you want the screw to go. Regarding this, how far should screw go into wood? The general rule of thumb is that the screw should enter at least half the thickness of the bottom material, e.g. 3/4″ into a 2 x 4.What is the difference between a lag bolt and a lag screw?They differ from lag screws because they thread their way through the wood as they’re screwed in, whereas lag screws require you to drill a hole first. Also, lag screws take advantage of a nut on one side to help hold things together; the tight fit of the wood screw negates the need for a nut.