Information on the most widely used ASTM standards within the materials testing industry
Introduction to ASME B107.300: Assembly Torque Tools
ASME B107.300 standard is for the physical design and manufacturing of adjustable and preset torque-indicating and torque-setting hand tools—commonly known as torque wrenches and torque screwdrivers.
Purpose: 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.
Key Requirements and Test Methods (The "ASME B107.300 Test")
When people refer to a tool "being tested to ASME B107.300," they are typically referring to the suite of performance proof tests mandated by the standard. These are type tests or design qualification tests, usually performed by the manufacturer on samples of a production run.
The main tests include:
1) Proof Load Test (The Primary Safety Test) Objective: To verify the tool can withstand repeated use at its maximum rated capacity without taking a permanent set (deforming) or failing. Procedure: The tool is secured in a fixture. A torque equal to 110% of the tool's maximum scale rating is applied in the tightening direction. This load is applied and released for a specified number of cycles (e.g., 100 cycles). Pass/Fail Criterion: After the test, the tool must show no permanent deformation or damage that would affect its calibration, function, or safety. For a click-type wrench, the "click" mechanism must still function correctly. |
2) Over-Torque Test (The "Abuse" Safety Test) Objective: To ensure the tool has a safety margin and will not catastrophically fail (e.g., shatter) if grossly overloaded, which could injure the user. Procedure: A torque significantly above the proof load (often 200% or more of maximum rating, as specified in the standard's tables) is applied once in the tightening direction. Pass/Fail Criterion: The tool must not exhibit "sudden or violent failure." It is allowed to deform or break, but it must do so in a controlled, non-explosive manner (e.g., a handle may bend, but it should not shatter sending pieces flying). |
3) Reverse Torque Test Objective: To verify the tool's strength when force is applied in the loosening direction (which is not the intended use for most tools). Procedure: A specified percentage (e.g., 30%) of the tool's maximum rating is applied in the reverse (loosening) direction. Pass/Fail Criterion: No permanent set or damage affecting function. |
4) Setting and Locking Mechanism Tests (for adjustable tools) Objective: To verify that the adjustment and locking mechanisms (the lock collar on a micrometer click wrench) function securely and do not slip under vibration or load. Procedure: The tool is set to a value and subjected to operational cycling and vibration simulation. Pass/Fail Criterion: The setting must not change beyond a very small, specified tolerance. |
5) Dimensional and Marking Requirements The standard also specifies requirements for: Clear, permanent marking of the manufacturer, model, serial number, and torque range/units. Scale markings and their legibility. General workmanship (freedom from burrs, sharp edges, etc.). |
This is the most important concept for users of the standard:
| ASME B107.300 | ISO 6789-2 (or ASTM E2428) |
|---|---|
| Manufacturing & Safety Standard | Calibration & Metrology Standard |
| Answers: "Is the tool strong and safe?" | Answers: "Is the tool accurate and precise?" |
| Focus: Structural Integrity & Safety Factor | Focus: Measurement Accuracy & Uncertainty |
| Tests: Proof Load, Over-Torque, Cycle Life | Tests: Error, Repeatability, Reproducibility |
| Performed by the Manufacturer (design/QC) | Performed by the User/Metrology Lab (periodic calibration) |
In Practice: A quality torque wrench is designed and built to meet ASME B107.300 (for safety/durability) and is then calibrated according to ISO 6789-2 (for accuracy). The calibration lab's equipment (torque testers) is itself calibrated traceable to national standards (like NIST).Relationship to ASME B107.100: B107.100 covers basic non-adjustabletorque tools (like fixed beam wrenches). ASME B107.300 is the more comprehensive standard for sophisticated adjustableand indicatingtorque tools.
4. Practical Application: Who Uses It and Why?
Tool Manufacturers: This is their design and quality control bible. They use it to engineer tools that meet a recognized safety benchmark and perform these tests to certify their product lines.
Procurement & Quality Engineers (End Users): When writing specifications for purchasing torque wrenches (e.g., for an aerospace, automotive, or energy company), they will often include the requirement: "Tools shall be designed and manufactured to meet the performance requirements of ASME B107.300." This ensures they are buying robust, safe tools.
Safety and Regulatory Personnel: The standard provides an objective basis for ensuring tools in the workplace won't fail dangerously under normal or abusive conditions.
ASME B107.300 is the critical performance and safety standard for the manufacturing of torque wrenches and screwdrivers. It defines rigorous mechanical tests—primarily the Proof Load and Over-Torque tests—to ensure tools are durable and have a safe failure mode. Compliance with B107.300 is a key indicator of a well-manufactured tool, but it must be paired with a separate calibration standard (like ISO 6789-2) to ensure the tool's measurement accuracy.
Related Standard
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.
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.
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