Fibres are obtained from natural sources such as cotton, wool etc. Yarn is obtained by braiding different fibres together.

Failure of a threaded fastener during assembly generally occurs in one of three modes:

• Failure by tensile fracture through the shank or threaded section of the fastener.
• Shear failure through the thread profile (thread stripping) of the external thread.

Three are parallel (UN/UNF, BSPP, metric parallel) and three are tapered (NPT/NPTF, BSPT, metric tapered). Three are pipe threads (NPT/NPTF, BSPT, BSPP) and three are not (UN/UNF, metric parallel, metric tapered). Keep in mind that tapered does not necessarily mean it is pipe thread (for example, metric tapered).

1. Determine if the thread is straight (parallel) or tapered. The thread is tapered if the diameter increases or decreases.
2. Measure the thread diameter.
3. Determine the number of threads per inch (TPI) or the pitch (metric threads) with the thread gauge.
4. Determine the thread standard.

Take out a yarn from a piece of cotton fabric. Now, press one end of the yarn with your thumb. Scratch the other end of the yarn along its length with your nail. You can see, the yarn splits up into thin strands.

The cotton wool is obtained from cotton plants. From the cotton bolls cotton is picked by hands. Fibres are then separated from the seeds by combing. This process is called ginning of cotton.

Winnowing: The process of separating heavier and lighter components of a mixture by wind or by blowing air is called winnowing. This method is used by farmers to separate lighter husk particles from heavier seeds of grain.

3. Looms are used for weaving yarn to make a fabric. There are two types of looms: handlooms and powerlooms. A loom that is worked by hand is called a handloom, and a loom that works on electric power is called a powerloom.

Water is a major constituent of all bodily fluids such as blood and plasma. Water is essential for digestion of food, absorption of food and also excretion of wastes from the body. Water is useful to cool the body and regulate temperature. When it is hot, we sweat from our skin.

Surface water is the largest source of water on the surface of earth. When water evaporates due to t… he heat, water vapours are formed. These vapours condense to form tiny droplets. As the number of tiny droplets of water increases, they come together to form large sized drops of water.