I am building some industrial style shelving for my office. Basically I need to know how much weight can one 2 inch screw in a stud hold? This will answer my question. Thanks.
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How much load a screw can hold does not depend on its length, assuming it is long enough. Instead, the load is a function of its cross-sectional area. A typical range for proof strength for steel is 50 to 100 kpsi (i.e., a screw with a 1 square inch cross-sectional area of steel can hold up to 50,000 to 100,000 pounds).
Of course, as the diameter of your screw increases, the stud is likely to fail first.
Assuming you mean a standard #8 wood screw, and a standard office, not much. A 2 inch drywall screw will hold even less.
The first half inch of most screws are tapered and thus don't add much to it's strength. Then you need to subtract the thickness of the bracket and the drywall. So now we have a whole one inch actually used for support. Enough to keep things tipping over but not enough to hold anything heavier than a picture up. And if you overtighten it into the wood it's more of a pin than a screw.
Offices often have commercial steel-stud walls. Bad news for you as steel studs are designed to hold up drywall and nothing else. They are thin sheet metal.
"Industrial-style shelving" implies industrial-style loads. Get a self-standing model from any shipping or warehouse supplier.
And the reason drywall screws hold less weight is because they are intended for one (and only one) purpose - holding drywall to steel studs. They are hard, thin, brittle and will snap off if overloaded.