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Considering this, what are lag screws used for?
Also commonly known as lag bolts, lag screws are some of the toughest fasteners. These extremely sturdy fasteners are usually used to connect heavy lumber or other heavy materials that are bearing an intense load. These screws differ from normal wood, self-drilling or sheet metal screws.
Likewise, people ask, 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.
A single 1/4" Grade 5 lag bolt, in a configuration like this, will fail at roughly 13,000 lbs. Even 1/8" lag screws (well down into "numbered" screw sizes) will have a shear strength of over 3,000 pounds.