Structurally rated lag bolts screws are available, but most home centers carry generic versions of varying quality. Grade 2 - Low Carbon Steel - up to 3/4" proof load 55000 psi, minimum tensile strength 74000 psi - 3/4" - 1/1/2" proof load 33000 psi, minimum tensile strength 66000 psi; Grade 5 - Medium Carbon Steel, Quenched and Tempered - up to 1" proof load 85000 psi - 1" - 1/1/2" proof load 74000 psi, minimum tensile strength 105000 psi A bolt, on the other hand, is not self-tapping and requires a nut to stay secure.Screws and bolts also differ in shape and cost — screws are often tapered, while bolts are not, and bolts tend to cost more than screws.Yes, bolts provide greater holding strength than screws. Blog Material matters.There are some materials that could require either a screw or a bolt assembly for fastening. A Other names for an Allen key screw include Allen bolt, socket screw and Knowing when to use bolts instead of screws, or vice versa, can be a challenge until you have more experience. Bolts are also best when the finished project is meant to be assembled and disassembled easily.Whether you’re using sheet metal, wood, concrete or drywall for your DIY undertaking, you want to think about how it applies to bolts vs. screws. 307A is the indication of the strength of the bolt.