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ISO 6789 Hand torque tools calibration and measurement

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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.


ISO 6789-1: Assembly tools for screws and nuts — Hand torque tools

Part 1: Requirements and methods for design conformance testing and quality conformance testing: minimum requirements for declaration of conformance

ISO 6789-2: Assembly tools for screws and nuts — Hand torque tools

Part 2: Requirements for calibration and determination of measurement uncertainty


Core Overview

ItemDetails
ScopeHand torque tools for controlled tightening; Type I (indicating) and Type II (setting)
Test TypesDesign conformance, quality conformance, recalibration
Measuring Range20%–100% of max torque (20%–100% of full scale)
TolerancesType I: ±1.5% (up to 100 N·m) / ±2% (over 100 N·m); Type II: ±3% (A/D/G classes)
Key Sections

ISO 6789‑1 (testing/marking); ISO 6789‑2 (calibration/uncertainty)


Test Procedures (ISO 6789‑1:2017)

1. Pre‑test Preparation

Environment: 18–28°C, ≤90% RH; 1‑hour temperature stabilization.

Torque tester: Uncertainty ≤0.5% of reading; traceable to national standards.

Pre‑loading: 3 cycles at 100% max torque to stabilize the tool.

2. Test Points & Sequence

Test 3 points: 20% (min), 60% (mid), 100% (max) of full scale.

5 measurements per point (15 total); load speed ≤10 N·m/s (last 20% ≤5 N·m/s).

No parasitic forces/moments; record peak torque at tool indication or click.

3. Tolerance Criteria

Type I (indicating): ±1.5% (≤100 N·m) or ±2% (>100 N·m) of reading.

Type II (setting): ±3% of set torque (A/D/G classes).

Reject if any measurement exceeds tolerance; repeat after adjustment if needed.

4. Marking Requirements

Brand, model, serial number, max torque, drive size, accuracy class, and ISO 6789 conformance.

Type I scales: Zero mark; graduation increments ≤5% of max torque.


Typical Use Cases

Automotive assembly, aerospace, heavy equipment, and general manufacturing requiring repeatable torque control (e.g., engine bolts, structural joints).


Related standard: 

ISO 1174-1: Assembly tools for screws and nuts — Driving squares Part 1: Driving squares for hand socket tools.

ASTM E2428: Standard Practice for Calibration and Verification of Torque Transducers

JIS B 4652: Hand torque tools -- Requirements and test methods.

Related Standard

ASME B107.300 Hand Torque Tools and Torque Testers

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.

ASTM E2428 Calibration of Elastic Torque Measurement

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 Hand socket tools test 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. 

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