ISO 2061:2015

Overview

ISO 2061:2015 - Textiles: Determination of twist in yarns - Direct counting method specifies a standardized laboratory procedure to measure the direction of twist, the amount of twist (expressed as turns per unit length), and the change in length on untwisting using a direct counting technique. The method applies to single yarns (spun and filament), plied yarns, and cabled yarns, and is designed primarily for yarns on packages (with special precautions for yarns taken from fabrics).

Key topics and technical requirements

• Principle: Remove twist by rotating one clamp relative to the other until yarn components are parallel and record revolutions to calculate turns per unit length.
• Apparatus: A twist counter with adjustable clamps (testing lengths 10 mm to 500 mm), a revolution counter, means to apply tension, a low-friction movable clamp (for length change), dissecting needle, and magnification equipment. Accuracy for length measurement: ±0.5 mm or ±2%, whichever is smaller.
• Specimen lengths:
  • Single spun yarns: typical initial lengths (e.g., cotton 10 and 25 mm; worsted and woolen 25 and 50 mm; bast fibres 100 and 250 mm).
  • Single multifilament / plied / cabled yarns: 250 mm if nominal twist > 1 250 turns/m; 500 mm if < 1 250 turns/m.
• Conditions: Testing in a standard atmosphere per ISO 139 (moisture equilibrium). Tension during sampling and testing must be the lowest practicable.
• Scope limits: Not suitable for monofilaments, open-end spinning products, intermingled (interlaced) multifilament yarns, yarns that stretch more than 0.5% when tension increases from 0.5 cN to 1.0 cN per tex (unless agreed special conditions), or yarns too large to clamp without distortion.
• Results and calculations: Average twist per specimen/sample, variation, change in length on untwisting, and twist factor (α) are defined and reported. Separate procedures and calculation notes are provided for single, plied, and cabled yarns (including methods to assess component twists).

Applications

• Quality control and acceptance testing of yarn twist for spinning, plying, and cabling operations.
• Process troubleshooting (e.g., diagnosing inconsistent twist in production).
• Product specification and verification for textile manufacturers and suppliers.
• Research and development in yarn design and performance testing.
• Contract and independent textile testing laboratories.

Who uses this standard

• Yarn and fibre manufacturers
• Textile testing laboratories and quality managers
• Textile technologists and R&D engineers
• Standards bodies and specification writers

Related standards

• ISO 139 - Standard atmospheres for conditioning and testing
• ISO 2 - Designation of the direction of twist in yarns
• ISO 1890 and ISO 7211‑4 - standards referenced for specific materials and related twist testing contexts

Keywords: ISO 2061:2015, twist in yarns, direct counting method, twist measurement, plied yarns, cabled yarns, twist factor, turns per metre, textile testing.