Yarn Spinning: Yarn Twist & Ply
No matter the spinning system employed, all yarns contain twist to hold the fibers together. The frictional forces created by the twist are the means by which all yarns are held together.
Most single yarns will be produced with a “Z” twist. That means the helix angel is the “Z” direction. Sometimes “S” yarns will be produced for special technical reasons. An “S” twist yarn’s helix angle is in the “S” direction.
Because of its mechanical design, yarns produced on the OE system will always be “Z” twist yarns.
Both ring and air-jet spinning systems can be set up to produce an “S” twist when it is required.
Twist Multiple (TM) is a common way of designating how much twist a yarn contains. TM is a relationship between yarn number (or count) and the turns per inch in the yarn. Using number English or cotton count, that relationship is represented as follows:
TM = TPI√ Ne.
Where TM is twist multiple, TPI is turns per inch, and Ne is number English (or cotton count).
Twist level may also be expressed in other ways, such as turns per meter. When communications between parties involve twist, it’s important to know the terms and units being used.
All yarns are originally spun as single yarns, but for certain end uses, single yarns may be twisted together to produce a ply yarn. Most common are two-ply yarns, formed by twisting two single yarns together. The plying twist is in the opposite direction of the singles twist. That means most ply yarns will contain an “S” twist.
Ply yarns are used where extra strength and evenness are required.
When a yarn is plied, the ply can be indicated in the yarn number.
A single yarn and a plied yarn may have the same effective yarn count, but the plied yarn would be made up of two singles yarns which are half the size of the final, total yarn count.
For the English Cotton Count yarn numbering system, a singles yarn would be written with the count/1 while a doubles or plied yarn would be written with the size/2.
For two yarns both equaling an Ne 24 yarn number, in which one yarn was a singles or un-plied and the second yarn was a doubles or 2-ply, the singles yarn would be written Ne 24/1 and the doubles yarn would be written Ne 48/2. These would be read out loud as “24 singles” or “48 doubles.”
Remember that English Cotton Count is an indirect yarn numbering system, and so an Ne 48/1 yarn would be half the size of an Ne 24/1 yarn. Two Ne 48/1 yarns plied together would have an equivalent count to a Ne 24/1 yarn.
TERMS TO KNOW (click to flip)
The fibers in the yarn form the center of the letter S, moving from lower right to upper left. This…view in glossary
The fibers in the yarn form the center of the letter Z, moving from lower left to upper right. This…view in glossary
The ratio of turns of twist per inch to the square root of the yarn size in Ne.view in glossary
The number of turns of twist in one inch of yarn. TM-twist multiple is derived from the TPI and the…view in glossary
A yarn formed by twisting two or more single yarns together.view in glossary
Also referred to as Ne or Number English. An indirect method of expressing the size of a cotton yarn (as…view in glossary
Common yarn numbering system used in North America for short staple, spun yarns (i.e., Ne=hanks/pound, 1 hank= 840 yards).view in glossary