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ASME B32.5-1977 (1994) — Preferred Metric Sizes for Tubular Metal Products Other Than Pipe
📐 ASME B32.5-1977 (ANSI B32.5-1977, reaffirmed 1994) is the metric-size standard that the ASME B32 Committee developed for tubular metal products other than pipe. It establishes preferred series of metric outside diameters, distances across flats, wall thicknesses, and lengths, covering outside diameters from about 0.12 mm to 320 mm, across-flat sizes from 10 mm to 400 mm, and wall thicknesses from 0.050 mm to 60 mm. Its companion standard, B32.6, provides preferred metric equivalents for the most commonly used inch sizes. Pipe products are excluded from this standard because they fall under the jurisdiction of the ANSI B36 Committee. The source PDF also includes an errata sheet issued in January 1996.
💡 Tubular products are normally ordered by specifying outside dimension and wall thickness; the standard also allows ordering by inside dimension and wall thickness, or by outside and inside dimensions, all within the tabulated sizes.
1. Scope and General Framework 📌
The scope and boundaries of the standard are as follows:
- Product form: tubular metal products other than pipe, including round, square, and rectangular tubes and other shaped sections.
- Outside diameter: about 0.12–320 mm for round tubes.
- Across flat: about 10–400 mm for square and rectangular tubular products.
- Wall thickness: about 0.050–60 mm; for square and rectangular tubes the preferred range is normally 0.30–20 mm.
- Length: a preferred series of straight lengths (non-coil), e.g., 1000, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 6000, 8000, 10000, 12000, 14000, 16000, and 18000 mm.
Consistent with the rest of the B32 series, the standard does not preclude sizes outside the series where precise engineering requirements dictate them, but encourages the tabulated preferred sizes for general-purpose applications to promote interchangeability, reduce inventories, and improve the availability of warehouse stock. Not every size is produced in every metal and grade; producers or distributors must be consulted. The development process reflects broad industry consensus: Subcommittee 4 (tubular metal products), formed on October 24, 1973, drew members from the American Iron & Steel Institute, the Copper Development Association, the Motor Vehicle Manufacturers Association, the Metal Cutting Tool Institute, and companies such as Babcock & Wilcox and Ford; its work combined ISO preferred numbers, sizes actually used in metric countries, and rounded metric equivalents of high-activity inch sizes. The proposal received Standards Committee B32 approval on March 30, 1977, and was approved as an American National Standard on September 7, 1977.
⚠️ Scope boundary: B32.5 covers only tubular metal products “other than pipe.” Fluid-conveying pipe and its size system are governed by the ANSI B36 Committee standards (e.g., ASME B36.10/B36.19); do not mix the two systems.
2. Preferred Size Series and Erratum 📏
Table 1 gives representative preferred outside diameters (mm) for round tubes: 0.12, 0.16, 0.20, 0.25, 0.30, 0.40, 0.50, 0.60, 0.80, 1.0, 1.2, 1.6, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 8.0, 10, 12, 14, 15, 16, 18, 19, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45, 50, 54, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 220, 250, 280, 300, and 320. Table 2 lists preferred wall thicknesses, with representative values including 0.050, 0.060, 0.080, 0.10, 0.12, 0.16, 0.20, 0.25, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0, 1.1, 1.2, 1.4, 1.5, 1.6, 1.8, 2.0, 2.2, 2.5, 2.8, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 7.0, 8.0, 9.0, 10, 11, 12, 14, 16, 20, 25, 30, 32, 35, 38, 40, 42, 45, 50, and 60.
| Table | Content | Representative steps (mm) |
|---|---|---|
| 1 | Preferred outside diameters, round tubes | 0.12–320, R10 progression |
| 2 | Preferred wall thicknesses | 0.050–60 |
| 3 | Across-flat sizes, square and rectangular tubes | 10–400 |
| 4 | Preferred lengths | 1000–18000 |
🚨 Erratum: the PDF includes an ASME errata page dated January 1996 for ANSI B32.5-1977 (R1994): on page 2, Table 2 (preferred wall thicknesses), the fourth entry of the first column is corrected from 0.01 to 0.10. Always use the corrected value 0.10 mm when referencing that table — never 0.01 mm.
Basis of tables: most preferred sizes derive from the R10 series of preferred numbers (ANSI Z17.1), with a few sizes from the R20 and R40 series; some deviation occurs from rounding and demonstrated or anticipated needs. A note under Table 2 states that the preferred wall-thickness range for square and rectangular tubular products is normally 0.30–20 mm. The outside-diameter stepping is denser in the small sizes (e.g., 12, 14, 15, 16, 18, 19, 20, 22) and widens toward the large end (e.g., 200, 220, 250, 280, 300, 320), reflecting both manufacturing practice and the geometric logic of the preferred-number system. The standard remains a convenient ordering reference for metric tubing even today, since it presents one consolidated set of preferred steps that designers, buyers, and stockists can share.
3. Engineering Practice Points 🛠️
- 🔍 Ordering method: prefer the “outside dimension + wall thickness” combination; “inside dimension + wall thickness” or “outside + inside” is also permitted, provided the combination falls within the tabulated sizes.
- 📦 Inventory consolidation: converge near-identical specifications onto one preferred step; compare with supplier stock lists and prefer available “preferred” sizes.
- 🔧 Tolerance pairing: B32.5 specifies nominal sizes only; outside-diameter and wall-thickness tolerances come from the governing material standards (e.g., ASTM/ISO tube specifications) and must be paired during selection.
- 🔄 Edition and erratum: the January 1996 erratum corrects Table 2; any citation of that table must use the corrected 0.10 mm value.
- 📋 Inch linkage: when metric equivalents of inch sizes are needed, consult the companion standard B32.6 (preferred metric equivalents for the most commonly used inch sizes).
4. FAQ ❓
❓ Q: How do B32.5 and B32.6 divide the work?
A: B32.5 defines the metric preferred size series (outside diameter, wall thickness, across flat, length); B32.6 provides preferred metric equivalents for the most commonly used inch sizes. They are companion standards used together.
A: B32.5 defines the metric preferred size series (outside diameter, wall thickness, across flat, length); B32.6 provides preferred metric equivalents for the most commonly used inch sizes. They are companion standards used together.
❓ Q: How do square and rectangular tubes differ in use from round tubes?
A: Square and rectangular tubes are specified by across-flat size plus wall thickness, with a narrower preferred wall range (normally 0.30–20 mm), and are generally supplied as straight lengths; select combinations within Table 3 across-flat steps and Table 2 wall-thickness steps, and watch the boundary with structural shapes standards.
A: Square and rectangular tubes are specified by across-flat size plus wall thickness, with a narrower preferred wall range (normally 0.30–20 mm), and are generally supplied as straight lengths; select combinations within Table 3 across-flat steps and Table 2 wall-thickness steps, and watch the boundary with structural shapes standards.
❓ Q: Is there a formal interpretation channel for this standard?
A: Early B32-series editions generally do not issue written interpretations (B32.3M’s title page states that no addenda or written interpretations will be issued for that edition); for clarifications, submit a formal interpretation request in writing to the B32 Committee Secretary under current ASME procedures.
A: Early B32-series editions generally do not issue written interpretations (B32.3M’s title page states that no addenda or written interpretations will be issued for that edition); for clarifications, submit a formal interpretation request in writing to the B32 Committee Secretary under current ASME procedures.
❓ Q: Why is pipe excluded?
A: Pipe falls under the ANSI B36 Committee, whose inch-based nominal size system (e.g., B36.10) differs in logic from the metric preferred series for tubing; hence B32.5 explicitly limits itself to tubular metal products other than pipe.
A: Pipe falls under the ANSI B36 Committee, whose inch-based nominal size system (e.g., B36.10) differs in logic from the metric preferred series for tubing; hence B32.5 explicitly limits itself to tubular metal products other than pipe.
❓ Q: What exactly does the Table 2 erratum change?
A: The January 1996 erratum corrects the fourth entry of the first column of Table 2 (preferred wall thicknesses) from 0.01 to 0.10 mm. The corrected value sits between 0.080 and 0.12, consistent with the R10 series logic.
A: The January 1996 erratum corrects the fourth entry of the first column of Table 2 (preferred wall thicknesses) from 0.01 to 0.10 mm. The corrected value sits between 0.080 and 0.12, consistent with the R10 series logic.
❓ Q: Does the standard include tolerances?
A: No. B32.5 specifies nominal preferred sizes only; outside-diameter and wall-thickness tolerances come from the governing material specifications and must be paired with the nominal sizes during selection.
A: No. B32.5 specifies nominal preferred sizes only; outside-diameter and wall-thickness tolerances come from the governing material specifications and must be paired with the nominal sizes during selection.
