Acetal Rod — Diameters, Lengths & Tolerances
Acetal rod is round bar stock produced from polyoxymethylene (POM), a precision engineering thermoplastic known for low friction, high stiffness, and excellent dimensional stability. These properties make acetal rod the preferred starting stock for machined bushings, gears, cams, rollers, and other close-tolerance mechanical parts that demand consistent performance in moving assemblies.
At a glance:
- Diameter range: 0.125" to approximately 6.0" (standard stock)
- Standard lengths: 2 ft and 4 ft cut lengths
- OD tolerance: close commercial tolerances maintained
- Material: Polyoxymethylene (POM) — acetal family
- Color: Natural (white/off-white); black available
- Low moisture absorption — excellent dimensional stability in humid environments
Standard Diameter Table
Acetal rod is stocked across a broad diameter range to support turning and milling operations:
| Diameter | Standard Lengths | Notes |
|---|---|---|
| 1/8" (0.125") | 2 ft, 4 ft | Small-diameter precision stock |
| 1/4" (0.250") | 2 ft, 4 ft | Standoffs, pins |
| 1/2" (0.500") | 2 ft, 4 ft | Bushings, spacers |
| 1" (1.000") | 2 ft, 4 ft | Gears, cams |
| 2" (2.000") | 2 ft, 4 ft | Larger machined components |
| 3" (3.000") | 2 ft, 4 ft | Heavy-section parts |
| 4" (4.000") | 2 ft | Large-bore applications |
Intermediate and non-standard diameters available upon request. Confirm current stock with Ready Plastics for exact size availability.
Mechanical Properties
Ready Plastics acetal rod is composed of polyoxymethylene offering these material characteristics:
| Property | Value |
|---|---|
| Density | 1.49 g/cm³ |
| Water absorption (24 h / 96 h) | 0.05 / 0.1 % |
| Flammability (UL 94) | HB |
| Heat deflection temp. (HDT, Method A) | 141 °C / 285 °F |
| Service temp. (long term) | 110 °C / 230 °F |
| Service temp. (short term) | 150 °C / 300 °F |
| Tensile strength | 53 MPa / 7,600 psi |
| Tensile modulus | 3,000 MPa / 435,000 psi |
| Flexural strength | 85 MPa / 12,000 psi |
| Flexural modulus | 3,000 MPa / 435,000 psi |
| Shore D hardness | 81 |
Spec values reflect the POM-H (acetal homopolymer) grade. See the Ready Plastics datasheet for grade-specific data.
Typical Applications
Acetal rod is machined into precision components across many industries:
- Bushings and sleeve bearings — low friction and wear resistance extend service life
- Gears and sprockets — high stiffness maintains tooth geometry under load
- Cam followers and rollers — excellent fatigue resistance in cyclic loading
- Standoffs and spacers — low moisture absorption preserves dimensional accuracy
- Valve components — chemical resistance supports fluid-handling assemblies
- Food-contact parts — FDA-compliant grades available for food and beverage machinery
Machining Acetal Rod
Acetal rod machines cleanly with standard carbide or high-speed steel tooling. It produces short, manageable chips and requires no special coolant, though compressed air or light cutting fluid helps remove chips in deep-bore or internal threading operations. Hold turning tolerances of ±0.001" routinely; tighter tolerances are achievable with care. Allow parts to equalize to ambient temperature before final inspection, as acetal can exhibit slight thermal expansion during cutting.