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D4693-07 – Standard Test Method Technical Guide
📐 Standard Overview and Scope
ASTM D4693-07 (Reapproved 2021) is a standard test method for evaluating low-temperature torque of grease-lubricated wheel bearings. It assesses the extent to which a test grease retards the rotation of a specially-manufactured, spring-loaded, automotive-type wheel bearing assembly when subjected to low temperatures. Torque values, calculated from restraining-force determinations, are indicative of the grease’s viscous resistance. This method is particularly effective for greases that produce torques less than 35 N·m at -40 °C.
The standard includes a warning about mercury, which is designated as a hazardous substance by regulatory agencies. Users must handle mercury-containing products with caution, refer to the Safety Data Sheet (SDS), and comply with local laws regarding sale and use. Additionally, the standard adheres to internationally recognized standardization principles as per WTO TBT Committee guidelines.
⚠️ Mercury Hazard Warning: Mercury and its vapor are hazardous to health and corrosive to materials. Follow applicable safety data sheets and regulatory requirements when handling mercury-containing products. Ensure legal compliance in your location.
⚙️ Test Method and Torque Measurement
The test method involves using a spring-loaded wheel bearing assembly that is subjected to low temperatures, specifically -40 °C. The restraining force required to rotate the bearing is measured, and the torque is calculated to determine the viscous resistance of the grease. The test is designed for greases that yield torque values less than 35 N·m at this temperature, ensuring compatibility with automotive wheel bearing applications.
Accurate temperature measurement is crucial, and the standard references several ASTM standards for thermometer calibration and specification, such as E1 for liquid-in-glass thermometers and E220 for thermocouple calibration. This ensures reproducibility and precision in test results.
| 🟦 Parameter | 📏 Specification |
|---|---|
| Test Temperature | -40 °C |
| Maximum Torque | Less than 35 N·m |
| Bearing Assembly | Spring-loaded, automotive-type wheel bearing |
| Torque Calculation Method | Restraining-force determination |
📊 Referenced Documents and Specifications
The standard references multiple documents that support the testing procedure, including ASTM standards and military specifications. These ensure consistency in grease properties, temperature measurement, and bearing specifications.
| 🟦 Standard | 📐 Description |
|---|---|
| D217 | Test Methods for Cone Penetration of Lubricating Grease |
| D3527 | Test Method for Life Performance of Automotive Wheel Bearing Grease |
| E1 | Specification for ASTM Liquid-in-Glass Thermometers |
| E77 | Test Method for Inspection and Verification of Thermometers |
| E220 | Test Method for Calibration of Thermocouples |
| MIL-G-10924F | Specification for Automotive and Artillery Grease |
💡 Technical Tip: Regular calibration of temperature sensors per ASTM E220 or E77 is recommended to maintain accuracy in low-temperature torque testing.
❓ Frequently Asked Questions
🔍 What is the primary purpose of ASTM D4693?
It determines the low-temperature torque of grease-lubricated wheel bearings, measuring the grease’s ability to resist rotation at low temperatures.
💡 What temperature is used for the test?
The standard test temperature is -40 °C, with torques typically less than 35 N·m for developed greases.
⚡ How are torque values derived?
Torque values are calculated from the restraining force needed to rotate the bearing assembly, representing the grease’s viscous resistance.
📌 What type of bearing is specified?
The test uses a specially-manufactured, spring-loaded, automotive-type wheel bearing assembly.