Drawn-over-mandrel tubing

What DOM means

National Tube Supply applies its DOM table tolerances to one pair at a time. The options are OD × wall, OD × ID or ID × wall. Its ID tolerances apply when the order includes ID. DOM describes drawing welded tube over a mandrel. Specify and inspect the bore size, shape and surface needed for the actual fit. National Tube Supply dimensional notes

Drawn-over-mandrel (DOM) describes a processing route for mechanical tubing, not a steel grade. Steel Tube Institute describes carbon or alloy electric-resistance-welded tube with flash removed, subsequently cold drawn through dies and over a mandrel to establish finished dimensions. Additional thermal treatment may follow drawing. STI, Drawn Over Mandrel overview

DOM is not seamless tubing. A smooth bore or an inconspicuous seam does not change the welded starting route. Plymouth explicitly describes its DOM offering as electric-welded mechanical tubing and lists cold-drawn seamless tubing as a separate product. Plymouth DOM product page

Specification and supplied condition

ASTM's active listing is A513/A513M-25, Electric-Resistance-Welded Carbon and Alloy Steel Mechanical Tubing, updated May 19, 2025. Plymouth identifies its DOM offering with A513 Type 5; the type number should not be mistaken for a steel grade or an edition suffix. Confirm the complete ordered designation and edition. ASTM publisher record; Plymouth specification section

Webco lists distinct delivery options including as-drawn, stress-relieved and normalized annealed, alongside special inside-diameter and bright finishes. These descriptions address different characteristics and should be recorded explicitly rather than combined into an assumed default. Webco DOM delivery conditions

Cold drawing can increase strength through work hardening, while subsequent processing changes the basis on which properties are supplied. Do not assign an as-drawn tensile value to thermally treated stock without applicable evidence. Likewise, a grade such as 1020 is not enough to select a mechanical-property row. Plymouth process description; STI thermal-treatment qualification

Where mechanical properties govern, specify the acceptance values and testing basis for the actual grade, size and condition. Preserve the distinction between catalogue typical data, contractual requirements and measured lot results. A hardness reading cannot independently establish untested toughness, fatigue behavior or weld performance.

Ordering dimensions and surface requirements

For round tube, OD, ID and wall thickness are related by the ideal concentric geometry ID = OD − 2t. That relation does not mean three independently specified nominal dimensions can be given arbitrary tolerances without checking compatibility. Tell the producer which dimensions and surfaces control the application.

Identify whether a wall requirement is nominal/average or a minimum acceptance requirement. Webco's size matrix explicitly labels its wall columns average wall. A marked size combination therefore does not by itself establish a guaranteed minimum wall or a pressure-design allowance. Webco DOM size chart

Define surface texture, defect acceptance and any machining or honing allowance separately. “Smooth ID” is not a complete hydraulic-cylinder bore specification. Agree the measurement method and required stage of acceptance if cutting, machining, bending or coating occurs later.

Producer examples and availability

Plymouth's current page lists its DOM range as 0.250–1.875 in. OD, 0.025–0.125 in. wall, maximum length 26 ft, with grades 1010–1020. These are that producer's advertised limits, not a rule that every OD/wall/grade/length combination can be supplied. Plymouth DOM specifications

Webco's separate size chart is a matrix of specific OD/average-wall combinations and asks purchasers to inquire about unlisted sizes. It is useful for a capability inquiry; it does not establish local inventory, the selected delivery condition or a component's mechanical rating. Webco size matrix

Processing and application qualification

STI lists DOM applications including bushings, hydraulic cylinders, vehicle components and frames. Those examples indicate common uses, not approval for an arbitrary pressure vessel, hydraulic assembly or competition chassis. STI application examples

For a pressure application, establish the governing equipment requirements, allowable material basis, actual wall acceptance, temperature, joints and inspection. Do not turn a general mechanical-tube product description into a working-pressure rating. For rotation, establish balance, runout, critical-speed and fatigue requirements separately from nominal straightness.

For forming or welding, qualify the actual grade, condition, geometry and joint. Define bend acceptance, local thinning, ovality and inspection where they matter. Review operations that can change the original cold-worked condition before reusing incoming-stock properties for the finished part. Keep material certification separate from fabrication qualification.

Bounded geometry example

Assume a round tube with 1.000 in. nominal OD and 0.120 in. nominal wall, a combination marked in Webco's chart. Ideal concentric ID is 1.000 − 2 × 0.120 = 0.760 in.; metal area is π/4 × (1.000² − 0.760²) = 0.3318 in². A hypothetical uniform axial load of 5 kip then gives nominal stress 5 / 0.3318 = 15.07 ksi. Webco size basis

This is original arithmetic on nominal geometry, not a load capacity or proof that the bore will measure exactly 0.760 in. It excludes dimensional tolerances, eccentric wall, defects, joints, bending, buckling, fatigue and design factors. Use the ordered acceptance geometry and applicable certified properties for a real design.

Source versions and release record

The inspected Webco chart prints ©2025, DOM SIZE RANGE CHART, 01/25. ASTM identifies A513/A513M-25. Plymouth, Webco's delivery page and STI are live pages without a technical issue date asserted here. Retain producer, heat/lot, grade, specification/edition, condition, dimensions and tolerances, inspection documentation and subsequent processing records with final-part acceptance.

See also Stock forms and dimensions.