YARN DIAMETER
Yarn diameter helps to determine how closely the yarns can be packed to make a fabric or how
well a given yarn will cover in a given fabric. Although yarn count serves the purpose of
defining yarn fineness, i.e., yarn diameter for general textile processing, sometimes it is essential
to calculate the exact diameter of the yarn.
In certain applications, yarn fineness expressed in diameter or thickness provides more useful
information. For example, determining the structural features of a fabric (e.g., cover factor, yarn
crimp, etc.) requires a prior knowledge of yarn diameter. It is important, therefore, to measure
yarn diameter or to provide an estimate of its value.
Yarn diameter is used to estimate fabric structural parameters such as width and cover factor.
Since thousands of ends or wales are presented side-by-side in the woven or the knit fabrics, a
slight change in yarn diameter can result in a substantial change in the overall cover factor of
fabric. Factors affecting yarn diameter are essentially those that affect yarn density or fiber
compactness.
For a given yarn count and at the same twist factor, the larger the fiber length, the higher the yarn
density and the smaller the yarn diameter.
Calculation of yarn diameter is specially needed in the following cases:
1. To set slub catcher or yarn clearer in winding.
2. To determine beam width, reed count, etc., in warping, sizing and weaving.
3. To decide number of threads per inch in cloth.
4. To decide needle size or machine gauge in knitting.
5. To study fabric geometry.
Relationship between yarn count ( Ne) and yarn diameter
The yarn shape is not cylindrical completely. The yarn diameter varies at different
places of the same count of yarn. It is not possible to find out the accurate yarn diameter of any
count of yarn. We can find approximate yarn diameter by calculation. The relationship between
yarn count ( Ne) and yarn diameter is given below:
Finding Yarn diameter of a given count of yarn:
Yarn Diameter from Count can be found out by extracting the square root of the total yards in a
pound of the given count and then subtracting 10 percent from the result. The yarn diameter in
inches is reciprocal.
The yarn diameter affects many technical settings of various processes. Slub catcher setting is
chosen according to yarn diameter. The yarn diameter greatly influences the decision-making
process of correct reed count selection in warping and weaving.
How to Calculate Yarn Diameter from Count
For example:
Find out the diameter of a 46s yarn.
Yards in a pound (840 x 46)
Square root 196.6
Less 10% 177.0
Hence the diameter of 1/177 inch
Fig: Estimating Yarn Diameter with Machine
In other words, if 177 threads are laid side by side they occupy one inch
The diameter of yarns vary as the square root of the yarn counts
Thus the diameter of 36s is 1/157 inch
And 16s is 1/104 inch
Note: When calculating yarn diameter from yarn count, a 10% reduction is applied to account
for the yarn's twist and fiber irregularities. This is because yarn count only measures the yarn's
linear density, not its thickness.
The 10% reduction is a standard industry practice to ensure accurate calculations. It considers the
following factors:
1. Yarn twist: Twisted yarns have a slightly reduced diameter due to the fibers being wrapped
around each other.
2. Fiber irregularities: Natural fibers like cotton, wool, or silk have inherent irregularities, which
affect the yarn's diameter.
By applying a 10% reduction, you get a more accurate calculation of the yarn's diameter, which
is essential for textile manufacturing, quality control, and product development.
Diameter per inch (cotton/spun silk) = √(yards per pound) – 10%
= 0.9 √yards per pound
= 26.1 √count
Calculation of yarn diameter from count is very useful particularly in weaving for determining
the optimum ends and picks per inch. Intersections of warp end for weft threads and weft threads
for warp have to be carefully considered. This is also useful for finding ends and picks while
changing from one count to another, for finding the counts in changing from one number of
threads per inch to another number of threads per inch, and for finding ends and picks per inch in
use and in changing from one pattern to another.
Example:
Find out the diameter of 20s count of yarn.
Solution:
Diameter per inch = √ ( yards per pound) – 10%
Here yards per pound = (20 x 840)
So, now
Diameter per inch = √(yards per pound) – 10%
= √ (20 x 840 ) – 10%
= 118 per inch (ANS)
