Sizes are H x W x wall (tube), leg x leg x thickness (angle, first leg vertical), thickness x width (flat bar).
Properties are computed with sharp corners. Real extrusions and formed tube have corner radii, so actual area,
weight and I are typically 2–8% lower. Use the supplier's values for critical designs.
S = I / c, the section modulus for bending stress: σ = M / S.
Tube X axis: load in the H direction. Flat bar flatwise: load through the thickness.
Angle Ix and Iy are about centroidal axes parallel to the legs, not the principal axes, which are at ~45° for equal legs.
Densities: aluminum 2.70, carbon steel 7.85, stainless 8.00 g/cm³. "Commonly stocked" is a rough guide;
steel tube walls 0.065/0.083/0.120" are 16/14/11 ga.