Information on the most widely used ASTM standards within the materials testing industry
ASTM E2428: Standard Practice for Calibration and Verification of Elastic Torque Measurement Standards
ASTM E2428 specify the procedure for the calibration and verification of elastic torque measurement standards.
Test Scope:
Primary application: Calibration of static elastic torque measurement standards (not for dynamic/high-speed torque calibrations or measurements)
Key exclusion: Dynamic torque applications (e.g., impact tools, high-speed rotational systems) – results from this practice cannot be directly applied to such scenarios
Core purpose: Establish a standardized method to verify the accuracy of torque transducers used for:
Calibrating torque testing machines (per ASTM E2624)
Validating torque tools like wrenches (supporting ISO 6789 compliance)
Ensuring traceability in torque measurements across manufacturing, aerospace, automotive, and metrology sectors.
| Equipment Type | Minimum Specifications | Purpose |
|---|---|---|
| Reference torque tester | Measurement uncertainty ≤0.5% of reading, with valid calibration certificate traceable to national/international standards | Provide the reference torque value |
| Loading mechanism | Capable of applying torque at controlled rates (≤10 N·m/s), with coaxial alignment | Ensure uniform loading without lateral forces |
| Data acquisition system | Resolution ≥0.1% of full scale, sampling rate sufficient to capture peak values | Record accurate torque measurements |
| Environmental controls | Temperature: 22 ±2°C (72 ±4°F), humidity: 45-55% RH | Minimize environmental effects on elastic elements |
Step-by-Step Test Procedure:
1. Pre-Calibration Preparation
Verify the reference torque tester's calibration certificate is current and within its validity period
Inspect the torque standard for damage, wear, or deformation that could affect accuracy
Allow the device to stabilize at ambient test conditions for ≥30 minutes
Zero both the reference tester and the torque standard to eliminate offset errors
2. Test Point Selection
Calibration must be performed at three mandatory torque levels:
20% of full scale (FS)
60% of FS
100% of FS
Optional additional points (e.g., 40%, 80% FS) may be added for enhanced characterization
3. Torque Application Protocol
Apply torque gradually and smoothly at a rate ≤10 N·m/s
For the final 20% of the range (80-100% FS), reduce the rate to ≤5 N·m/s to minimize dynamic effects
Hold each test torque for 5 seconds to allow elastic stabilization before recording
Repeat 5 times at each test point (clockwise and counterclockwise directions if bidirectional calibration is required)
Ensure no lateral forces or bending moments are applied during loading (critical for accuracy)
4. Data Collection & Analysis
Record the reference torque value and the torque standard's indicated value for each measurement
Calculate:
Average value for each test point
Deviation (indicated value - reference value)
Percent error (deviation/reference value × 100%)
Determine measurement uncertainty following GUM (Guide to the Expression of Uncertainty in Measurement) principles.
Acceptance Criteria:
Traceability: Calibration results must be traceable to SI units through a documented chain of calibrations
Uncertainty: Expanded uncertainty (k=2) of the torque standard must be ≤0.5% of reading (matching the reference tester's uncertainty)
Repeatability: Maximum variation between repeated measurements at any test point must be ≤0.2% of the reference value
Hysteresis: Difference between loading and unloading curves must be ≤0.3% of full scale (for bidirectional transducers).
Key Technical Requirements
1. Torque Rate Control
Critical parameter: Loading rate directly impacts measurement accuracy – excessive speed introduces dynamic errors in elastic elements
Standard requirement: ≤10 N·m/s for the main range, ≤5 N·m/s for the final 20%
2. Alignment Precision
Torque must be applied coaxially with the transducer's axis of rotation
Maximum allowable misalignment: 0.5° to prevent bending stresses that could affect elastic deformation measurements
Relationship to Other Standards
ASTM E2624: Directly references ASTM E2428 for calibrating torque transducers used in torque testing machine verification
ISO 6789: Relies on torque standards calibrated to ASTM E2428 for accurate hand torque tool testing (ASTM E2428 serves as the upstream standard for ISO 6789's calibration equipment)
ASME B107.300: Complements this standard for hand torque tool calibration requirements.
| Industry | Key Applications | Benefits |
|---|---|---|
| Metrology | Calibration of primary/secondary torque standards | Establishes national/international reference points for torque measurements |
| Automotive | Validation of torque testing machines for engine assembly | Ensures accurate bolt tightening in critical components (e.g., cylinder heads) |
| Aerospace | Calibration of torque transducers for aircraft maintenance | Maintains safety-critical fastener integrity |
| Manufacturing | Quality control of torque tools (wrenches, screwdrivers) | Supports ISO 6789 compliance for hand torque tools |
Related Standard
ISO 1174-1: Assembly tools for screws and nuts — Driving squares
Part 1: Driving squares for hand socket tools
ISO 1174-1 specifies the dimensions, separation force and designation of driving squares for hand socket tools.
ISO 6789 (now split into ISO 6789‑1:2017 and ISO 6789‑2:2017) is the global standard for hand torque tools, defining conformance testing, calibration, tolerances, and marking to ensure reliable torque control in bolted connections. It applies to indicating (Type I) and setting (Type II, e.g., click) torque wrenches, covering design validation, production quality checks, and recalibration. ISO 6789 is applicable for the step by step (static) and continuous (quasi-static) calibration of torque measurement devices, the torque of which is defined by measuring of the elastic form change of a deformable body or a measured variable which is in proportion to the torque.
ASME B107.300 establishes dimensional, performance, safety, and marking requirements for assembly torque tools. Its core purpose is to ensure that these tools are manufactured to be strong, durable, and safe for the user, providing a minimum performance benchmark for the industry.
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