Acetal Copolymer Tube — OD/ID Sizes, Tolerances & Ordering
Acetal copolymer (POM-C) tube is extruded hollow round stock, supplied in standard OD/ID combinations for applications requiring a hollow geometry. It is used as bushing blanks, sleeve stock, spacer tubes, and valve components. A practical advantage over Delrin (POM-H) tube: acetal copolymer does not develop the mid-wall or centerline porosity that can affect heavy-wall POM-H tube in large cross-sections. For hot-water-contact hollow components — valve sleeves, appliance tubes — POM-C is the preferred material over POM-H.
At a glance:
- OD range: 0.500" through 8.0" in standard wall thicknesses
- Standard length: 4 ft
- No centerline porosity concern in standard wall thicknesses
- OD tolerance: ±0.015"–0.030" (ASTM D6100)
- Wall tolerance: ±10–15% of wall
- Grade: standard natural (white) POM-C; FDA-compliant natural available with lot documentation
Why Use Acetal Copolymer Tube vs. Delrin Tube
Both POM-C and POM-H tube are used for the same bushing and sleeve applications. The decision factors:
Use acetal copolymer tube when:
- Hot-water contact (>140°F) is involved — POM-C's hydrolysis resistance is critical for dishwasher and hot-water valve sleeves
- The tube has a heavy wall (wall > 25% of OD) — POM-C is less prone to mid-wall porosity in thick-wall sections
- The application benefits from POM-C's slightly lower cost
- General-purpose sleeves and spacers where no fatigue advantage of POM-H is needed
Use Delrin tube when:
- The print specifies Delrin (POM-H) specifically
- Maximum fatigue performance is needed in the tube structure itself (unusual for tube applications, which are mostly static)
- Applications sensitive to the 10°C lower melting point of POM-C (rare in tube applications)
Standard Stocked Acetal Copolymer Tube Sizes
| OD | Nominal Wall | ID (approx.) | OD Tolerance | Length |
|---|---|---|---|---|
| 0.500" | 0.062" | 0.376" | ±0.015" | 4 ft |
| 0.625" | 0.062" | 0.501" | ±0.015" | 4 ft |
| 0.750" | 0.062" | 0.626" | ±0.015" | 4 ft |
| 1.000" | 0.125" | 0.750" | ±0.015" | 4 ft |
| 1.000" | 0.250" | 0.500" | ±0.015" | 4 ft |
| 1.250" | 0.125" | 1.000" | ±0.020" | 4 ft |
| 1.500" | 0.125" | 1.250" | ±0.020" | 4 ft |
| 1.500" | 0.250" | 1.000" | ±0.020" | 4 ft |
| 2.000" | 0.125" | 1.750" | ±0.020" | 4 ft |
| 2.000" | 0.250" | 1.500" | ±0.020" | 4 ft |
| 2.000" | 0.375" | 1.250" | ±0.020" | 4 ft |
| 2.500" | 0.250" | 2.000" | ±0.025" | 4 ft |
| 3.000" | 0.250" | 2.500" | ±0.025" | 4 ft |
| 3.000" | 0.375" | 2.250" | ±0.025" | 4 ft |
| 4.000" | 0.375" | 3.250" | ±0.030" | 4 ft |
| 4.000" | 0.500" | 3.000" | ±0.030" | 4 ft |
| 6.000" | 0.500" | 5.000" | ±0.030" | 4 ft |
| 8.000" | 0.500" | 7.000" | ±0.035" | 4 ft |
Non-standard OD/wall combinations available to special order.
Tolerances
OD tolerance: Per ASTM D6100; tabulated above.
Wall thickness tolerance: ±10–15% of nominal wall. For precision bore concentricity (eccentricity < 0.005" TIR), finish-bore the ID after procurement — as-extruded ID is suitable for most bushing applications but not precision instrument fits.
Straightness: 0.050"/ft standard; precision-straightened to 0.010"/ft on request.
Cross-section uniformity: Acetal copolymer tube cross-section is uniform and pore-free in standard wall thicknesses. Unlike heavy-wall Delrin tube, POM-C tube does not develop significant mid-wall porosity.
Applications for Acetal Copolymer Tube
Bushing and sleeve blanks: Cut tube to length; finish the ID to final bearing bore dimension. Saves material and boring cycle time compared to starting from solid rod.
Hot-water system components: POM-C tube in dishwasher spray arm hubs, hot-water valve sleeves, and appliance manifold sleeves. Hydrolysis resistance of POM-C is essential in these applications — Delrin tube is not appropriate.
Spacer tubes: Cut to length as spacers in bolted assemblies, pivot pins, and guided mechanisms.
Fluid coupling components: POM-C tube sections as coupling sleeves in fluid systems where light chemical exposure and moderate pressure are involved.
Irrigation system components: Valve body sleeves, filter housings, and manifold inserts in drip and sprinkler irrigation systems.
Machining Acetal Copolymer Tube
Chucking: Chuck on OD with standard three-jaw for heavy-wall tube; use an expanding mandrel or split collet for thin-wall tube to distribute clamping load without distortion.
Boring the ID: For precision bore, drill to 0.010" undersize, then single-point bore to final size. Achievable bore tolerance: ±0.001–0.002" with CNC boring. Ream for production bores: ±0.0005" tolerance achievable.
Facing and parting: Standard facing and cutoff operations; same speeds/feeds as solid acetal copolymer rod. See the acetal copolymer machining guide for parameters.
Ordering Acetal Copolymer Tube
Specify on your purchase order:
Acetal copolymer (POM-C) tube, [OD]" × [wall]" nominal, ASTM D6100 Type I, natural color. Standard 4-foot lengths (or cut to [X]" ± 0.125"). Certificate of conformance required.
For FDA-compliant tube: add "FDA 21 CFR 177.2480 compliance documentation required."
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