ISO 2061:2015 specifies a method for the determination of the direction of twist in yarns, the amount of twist, in terms of turns per unit length, and the change in length on untwisting, by the direct counting method.
This International Standard is applicable to
a) single yarns (spun and filament),
b) plied yarns, and
c) cabled yarns.
Separate procedures are given for each type of yarn. The method is designed primarily for yarns in packages, but, with special precautions, the procedures can be used for yarns taken from fabrics. It is not suitable for the determination of twist in a monofilament.
NOTE See also ISO 1890, which was prepared especially for the needs of glass textile technology, and ISO 7211‑4.
ISO 2061:2015 covers the determination of twist in plied and cabled yarns as follows:
a) in plied yarns: the final twist of the plied yarns and the original twist of the single yarn before plying;
b) in cabled yarns:
- ? the final cabling twist of the yarn;
- ? the original twist of the plied yarn after plying, but prior to the last stage of processing;
- ? the twist of the single yarn before plying.
If desired, the twist of single and plied yarn components, as they lie in the final structure, can be determined by the special procedure given in 10.5.7.
ISO 2061:2015 is not applicable, except by agreement, to yarns which stretch more than 0,5 % when the tension increases from 0,5 cN to 1,0 cN per unit linear density of the yarn expressed in tex. Such yarns can be tested under special conditions of tension which are accepted by all parties interested in the test results.
ISO 2061:2015 is not suitable for products of open-end spinning and intermingled (interlaced) multifilament yarns.
ISO 2061:2015 is not applicable to yarns which are too large to permit their being placed in the clamps of the testing apparatus without crushing or distortion severe enough to affect the test results.