Direct Answer
A camber diagram is a simple elevation view on the piece mark drawing showing the required upward curvature of the beam at midspan and at intermediate points. It specifies the midspan camber dimension (in inches), the camber profile shape (typically parabolic), and the tolerance. Read it by checking the midspan value first, then verifying the tolerance band stated in the general notes.
Full Explanation
Camber diagrams are usually simple: a baseline representing the theoretical straight beam, with a vertical arrow indicating the upward camber at midspan. The dimension (e.g., '3/4"' or '1-1/8"') is the midspan offset. Some drawings show intermediate camber points for very long or non-uniformly loaded beams. The general notes typically specify that camber will be measured under no load before erection. Fabricators should verify camber with a straightedge or optical level before shipping.
What This Means for Your Shop
If the mill delivers a cambered beam that reads 1" at midspan but the drawing requires 1.5", you either accept the deficiency (with engineer approval) or send the beam to a cambering shop. Cold-press cambering after receipt is common for standard sections.
Common Mistakes
Applying camber to beams that are too short (under 25 feet). Residual mill stress often provides some natural upward curvature in short beams, and specifying camber can result in over-cambering.
Recommended Process
After receiving cambered material, measure midspan camber with a string line or level on a flat surface. Record results against the drawing requirement. Flag any member outside tolerance before it enters the fabrication sequence.