The Straightened Fiber Method of Single Yarn Twist Testing Lab Report -8

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Name of the Experiment

Determination of yarn twist by using the straightened fiber method./ Study on single yarn twist tester.


The spinning process involves drafting and twisting strands of fiber in a parallel pattern on their own axis to form yarn. In order for fibers to be held together in a yarn, twist is vital. As defined by Skinkle, twist refers to the number of spiral turns given to a yarn to hold the fibers or threads together. Twisting in yarn is essential because it plays a important role in determining the characteristics of textile products. The twist is applied to individuals or groups of fiber that bind fiber to each other and hold them together. Without twists, the fibers may be easily separate from each other. The degree of twist is important for yarn strength, durability and uniformity of yarn. However, the amount of twist affects the key properties of yarn, such as stretch, elasticity, pilling resistance and appearance of the final product. The following are the different methods of determining the twist in the yarn.

  1. The straightened fiber method.
  2. The twist contraction method.
  3. The twist to break method.
  4. Optical method.
  5. Untwist method.

In this experiment we will use “The straightened fiber method” to determine the twist per inch for a single yarn.


  1. To know about twist of yarn.
  2. Come to learn the method of determination of twist.
  3. To know working procedure of single yarn twist tester.
  4. To know twisting calculation.


  1. Single yarn.
  2. Single yarn twist tester.
  3. Needle.
  4. Calculator.

Principle of “The straightened fiber method”:

This method is generally used to measure the amount of twist in single yarns. The principle involved here is that since twist is inserted into an element of yarn by the relative rotation of its two ends, the simplest method of measuring the twist is to reverse the process and count the number of turns required to untwist the yarn until the fibers become parallel. The method can be used for measuring twist in single yarns.

Machine Description:

Figure 01: Single yarn twist tester
A= Tensioning arrangement.B= Pulley.
C,D= Pillars.E= Black board.
F= Fixed jaw.G= Specimen.
H= LensI= Rotatable jaw
J= HandleK= Counter
L= Base 

The schematic diagram of single yarn twist tester is given in figure 01, the instrument is a simple one consisting of a fixed jaw  mounted on a pillar with a guide pulley and tensioning device. The other portion consists of a rotating jaw connected to a revolution counter which can be operated by a handle. The instrument is provided with a magnifying lens and a black board underneath the yarn.

Working procedure:

  1. To make the test, the revolution counter is set to zero, and the yarn is clamped into the rotating jaw.
  2. Then, it is led through the fixed jaw, over the guide pully, and tensioned by clipping a small weight onto it. Adjust, yarn length 10 inch. Then, the fixed jaw is closed, and the handle is rotated to remove the twist.
  3. Finally, the endpoint is judged by the eye with the help of a small lens, but greater precision can be obtained by using a dissecting needle.
  4. When most of the twist is removed, the needle is pushed through the fibers as close to the fixed jaw as possible and gently moved towards the rotating jaw.
  5. The final rotation, either a 1/4 twist or half a twist, can be adjusted with the dissecting needle in this position.
  6. Than, again re-twist the yarn until adjust the length.(10 inch)
  7. The number of turns given to untwist is read from the revolution counter and record.
  8. About 5 tests are conducted in this manner and the mean TPI is calculated.
  9. Noted that, at first we un-twist then we again re-twist the yarn. That’s why out total length will be 2L.


S/NTwist directionSpecimen Length (L)Counter Reading (R)TPI=R/2L
1.  S-Twist  250 mm ( 10 inch)532.65
                                                                                                Avg. TPI=2.63 about 3


TPI means twist per inch. That’s means, number of twist per inch. We tested 5 sample. Our avg. TPI is 3.


In the spinning industry, it is very important to calculate twist per inch (TPI) of a yarn. Now that we have done this experiment, we are able to calculate TPI of a yarn. This is going to be helpful to us in our careers. Thanks to our teacher for helping us.

More lab report:

  1. Working Principle of Knowles Balance.
  2. Working Principle of Beesley Balance.
  3. Working Principle of Quadrant Balance.
  4. Fiber fineness test sheffield micronaire: Air flow method.
  5. Fiber maturity by direct method: Caustic Soda Swelling Method.
  6. Fiber fineness test: Gravimetric Method

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