This International Standard specifies a method for the deter-mination of twist in textile glass continuous filament yarns and staple fibre yarns.
In the case of staple fibre yarns, the results obtained should be regarded as indicative only.
This International Standard does not apply to rovings.
Determination of the twist must take into account the fact that the run-out system may have an influence on the results. When the yarn is run out tangentially, this system does not induce any change in the twist level that was given by the twist frame. On the other hand, if the yarn is run out overhead, the measured twist level is modified, depending first on the winding direction, secondly on the length of wound wrap.
This change in relative value is small when twist is high and wrap length is long.
In practice, the twist found finally in a fabric may be rather dif-ferent from the twist of wound yarn.
The method specified in this International Standard allows the measurement of intrinsic twist of yarn on the bobin (tangential run out).
If, however, it is required to test by the overhead method, it is necessary to reduce any risk of variation caused, for example, by shelling of wraps. For this reason the bobin must be posi-tioned horizontally.
This International Standard concerns single yarn (one twist operation), folded (plied) and cabled yarns (two or more twist operations).
The method specified provides a measurement for each suc-cessive twist step.
If, for folded (plied) or cabled yarns, only the measurement of final twist step is required (general situation) the method specified for single yarn should be followed.