Round tubing

Identify the application and product specification

Atlas's A500 HSS 2.500 × 0.250 lists 2.500 in OD, 0.250 in nominal wall, 0.233 in design wall and 1.66 in² area. Using the ideal annulus formula with design wall gives 1.659 in². Nominal wall would give 1.767 in². Inspect actual diameter, wall and shape for fit. Atlas round HSS section table

Round tubing describes geometry, not one interchangeable material product. Mechanical tubing, structural hollow sections, hydraulic/instrument tubing and nominal-size pipe can have similar outside dimensions while carrying different grade, condition, testing and surface requirements. Select the governing product specification before comparing catalogue sizes.

ASTM A513/A513M-25 covers electric-resistance-welded carbon and alloy steel mechanical tubing. Its public abstract distinguishes as-welded, sink-drawn, drawn-over-mandrel and special smooth-ID types. By comparison, Atlas Tube identifies its A500/A1085 products as structural tubing. Those descriptions do not establish a pressure-system rating for an arbitrary piece. ASTM A513/A513M scope, Atlas structural HSS

A useful callout combines specification and edition, grade, production type, supplied condition, dimensional basis, length and inspection requirements. See Stock forms and dimensions.

OD, ID and wall: specify what is controlled

Use explicit outside diameter (OD), inside diameter (ID) and wall thickness, with units. For an ideal concentric circular tube, ID = OD − 2 × wall. That geometric identity does not mean all three dimensions have independent guaranteed tolerances.

National Tube Supply's DOM guide states that its tabulated tolerances apply simultaneously to only two of the three dimensions: OD×wall, OD×ID, or ID×wall. Its ID tolerances apply only when ID is part of the ordered dimensional basis. For example, its 0.500–1.699 inch DOM diameter row lists OD +0.005/−0.000 inch and ID +0.000/−0.005 inch, subject to that ordering qualification. Do not promise the listed ID tolerance on an OD×wall order. National Tube Supply dimensional notes

Check the applicable size and condition notes before applying any table. National Tube Supply, for instance, excludes normalized-and-tempered or quenched-and-tempered conditions from its listed hot-finished A519 diameter tolerances. A treatment or finishing change can alter the acceptance basis. National Tube Supply hot-finish tolerance exclusions

Nominal pipe size is a different naming system

Do not substitute “2-inch pipe” for 2.000-inch-OD tubing. Wheatland's energy-tubular brochure lists NPS 2 with 2.375-inch OD, including different wall options for that same OD. The nominal name is an identifier requiring a dimensional lookup, not a direct OD or ID measurement. Wheatland line-pipe tables

A common OD does not by itself establish compatible fittings, thread geometry, wall requirements or service qualification. Keep the complete product and connection description when transferring a drawing into a purchase order.

Welded, DOM and seamless routes

Plymouth explicitly describes its DOM mechanical tubing as electric-welded, with subsequent mandrel drawing. DOM is therefore not a synonym for seamless. Its named offering references A513 Type 5, grades 1010–1020, with published OD range 0.250–1.8750 inches, wall range 0.025–0.125 inch and maximum length 26 feet. These are producer capability ranges, not proof that every OD/wall/length combination is available. Plymouth DOM product

National Tube Supply separately lists cold-drawn and hot-finished seamless products under A519. Retain both route and condition; “cold drawn” alone does not identify whether the starting tube was welded. Supplier product-route descriptions

Structural wall thickness: a bounded example

Atlas's A500 round-HSS table lists HSS 2.500 × 0.250 with 2.500-inch OD, 0.250-inch nominal wall, 0.233-inch design wall, nominal weight 6.01 lb/ft and tabulated area 1.66 in². The column labels matter: design wall is not a report of a measured tube and nominal wall is not automatically the property-calculation thickness. Atlas A500 round-HSS section table

Original geometry check: using the ideal annulus formula A = π(Dt − t²), nominal wall gives π(2.5 × 0.250 − 0.250²) = 1.767 in². Using the rounded 0.233-inch design wall gives 1.659 in², consistent with the published 1.66 in² area. The difference is a calculation-basis distinction, not evidence that delivered material is underweight or out of tolerance. Use the applicable design standard and product table; do not apply this example's wall treatment to every tubing specification.

Neither this area nor the listed mass establishes member capacity. Connections, buckling, bending, restraints, load combinations and material requirements remain part of the structural assessment.

Fluid-service and handling boundaries

Swagelok's tubing guide ties fitting performance to specified tube material, hardness, surface condition and wall range. It does not recommend its tube fittings outside the listed wall ranges and states that allowable pressure ratings are generally calculated using ASME B31.3 stress values, except where noted. A pressure table must therefore be read with its alloy, temperature, wall and footnotes; it is not a rating of all round stock having that OD. Swagelok Tubing Data

The same guide cautions against dragging tubes across rough surfaces and calls for deburred ends to avoid damaging ferrule sealing edges. These are functional surface requirements, not merely appearance preferences. Protect relevant OD and bore surfaces through cutting, storage and assembly. Swagelok handling guidance

For a fluid system, obtain the exact tubing/fitting selection, compatibility and installation instructions. For a sliding or bearing fit, specify the controlled bore and finish. For a fabricated frame, specify the structural grade and weld details. These applications need different evidence even if the same diameter appears in each catalogue.

Editions and acceptance record

ASTM lists A513/A513M-25 as active, updated May 19, 2025. Swagelok's PDF footer identifies MS-01-107, Rev W, October 2023. Wheatland's brochure prints WET-041825; its 2017 upload directory is not the technical edition. Atlas's cited section-property PDF displays no technical revision date, and Plymouth's live product page is likewise undated. National Tube Supply displays an October 2, 2026 page-update timestamp, which does not independently establish the editions of every embedded standard table.

At receipt, reconcile specification/grade, route and condition, ordered dimensional pair, tolerances, length/end condition and heat/lot documentation. Resolve an unsupported substitution before machining or installation. Catalogue size availability and a round profile alone do not establish certification or fitness for service.