A500 vs A513

If the tube is a load-rated structural member — a column, brace, or frame element designed to a building code — specify A500 (or A1085). If the tube will be machined, press-fit, telescoped, or assembled into a mechanical component where dimensional behavior and surface condition control, specify A513. The two specifications qualify different things: A500 qualifies strength classes with tension and flattening tests; A513 qualifies process routes (Types 1–6) with the dimensional and surface expectations those routes imply.

Both cover round, square, and rectangular ERW product in overlapping sizes, which is exactly why they get confused on purchase orders.

A500's tolerances and mass provisions are appropriate to structural work and are looser than mechanical-tubing expectations; a bearing pressed into an A500 section will find that out quickly. Conversely, A513 carries no structural grade system — putting mechanical tubing into a code-governed structural member leaves the engineer without the certified strength basis the design assumed.

• A500: grades A–D certify strength; no process-route selection
• A513: Types 1–6 certify process routes; no structural strength classes
• A500 permits delivered mass below nominal — hence the reduced design wall convention
• Dual-specification product exists but must be certified to both, not assumed

Machine bases, guarding, and equipment frames often mix a code-checked A500 skeleton with A513 mechanical members where shafts, bushings, and fasteners need controlled fits. The drawing should call the specification per member, not per project. For the mechanical side of that conversation, see the companion A513 handbook at astma513.com.