PTFE balls, commonly used in applications requiring chemical resistance and low friction, have tolerances that vary based on size and precision requirements. Standard diameter tolerance is typically ±5%, while precision tolerances are specified per item. Larger diameter balls (e.g., above a certain threshold) often have a tolerance of ±0.005 inches with a maximum Total Indicator Reading (TIR) of 0.0005 inches, whereas smaller balls may have tighter tolerances of ±0.003 inches with a TIR of 0.003 inches max. Surface finishes also play a role, with tumbled finishes ranging from 50–63 microinches and machined finishes around 32 microinches. These specifications ensure performance in applications like valves, bearings, and seals.
Key Points Explained:
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Standard Diameter Tolerance (±5%)
- The baseline tolerance for ptfe balls is ±5% of the nominal diameter. This applies unless tighter precision tolerances are specified.
- Example: A 10 mm ball could range from 9.5 mm to 10.5 mm under standard tolerance.
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Precision Tolerances by Size
- Larger Balls: Typically ±0.005 inches with a TIR ≤ 0.0005 inches. TIR measures roundness deviation.
- Smaller Balls: Often ±0.003 inches with a TIR ≤ 0.003 inches, allowing for tighter control in compact applications.
- Why it matters: Tighter tolerances reduce wobble in high-precision systems like medical devices or aerospace components.
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Surface Finish Specifications
- Tumbled Finish: 50–63 microinches (Ra), suitable for general-purpose use.
- Machined Finish: ~32 microinches (Ra), preferred for smoother operation in sensitive environments.
- Purchaser tip: Smoother finishes may reduce wear but increase cost—balance requirements with budget.
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Application-Driven Considerations
- Chemical resistance and low friction make PTFE ideal for seals and bearings, but tolerance adherence ensures longevity.
- For dynamic applications (e.g., rotating valves), prioritize balls with lower TIR to minimize vibration.
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Customization Options
- Suppliers often offer tailored tolerances beyond standard specs. Document exact needs in RFQs to avoid mismatches.
- Example: A ±0.001-inch tolerance might be achievable for critical applications, though lead times and costs may rise.
By understanding these nuances, purchasers can select PTFE balls that align with operational demands while avoiding over-specification. Always verify tolerances with certified inspection reports, especially for regulated industries like pharmaceuticals or food processing.
Summary Table:
| Tolerance Type | Specification |
|---|---|
| Standard Diameter | ±5% of nominal diameter |
| Precision (Large Balls) | ±0.005 inches, TIR ≤ 0.0005 inches |
| Precision (Small Balls) | ±0.003 inches, TIR ≤ 0.003 inches |
| Surface Finish (Tumbled) | 50–63 microinches (Ra) |
| Surface Finish (Machined) | ~32 microinches (Ra) |
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