**3. Structure of bolt and nut assembly**

Bolt is not a bolt; it is a spring. When tightening a bolt in the assembly, it means tensioning or slackening a spring. Bolt is pulling the flanges together as a "bolt spring." "Bolt spring" force must pull the flanges together more than the forces acting to push them apart. If "bolt spring" is too loose, the pressure stretches the bolt, and the flange opens and leaks. Therefore, "bolt spring" should prevent the flanges from separating; therefore, bolts are preloaded (stretched).

Clamp load is the force that holds a joint together. In a threaded assembly, the clamp load is equal in magnitude to the tension of the bolt but opposite in direction. Bolt tension is achieved after some friction loss at bolt head and thread. This clamp load is very critical as a bolted joint is designed so that the external forces never overcome the clamp load, and this is the major reason fasteners are used (see **Figure 1**) [1].

**Figure 1.** *Forces acting on a "bolt spring."*

**119**

**5.1 Spring washer**

**Figure 3**) [1].

**5.2 Star washer**

*Liquid Thread Locking Solution for Machinery Assembly Industry*

Bolt tightening torque stretches bolt shank to at least 65% of its yield strength. Yield strength is the stress at which the bolt shank starts to stretch. If the stress is beyond this point, then the bolt shank will break. As shown in **Figure 2**, tightening torque elongates the bolt. Being an elastic material, elongated bolt wants to retract. That is when a bolt tension is generated and the spring force clamps parts together. Red marked area shows the max. clamp load. Typically, the acceptable clamp load is in the range of

For such a long history of mechanical fasteners, those people related to designing, assembly, and repair have built some mindset on their own for a long time, it has become a conviction, then belief, and then it has become a myth to them. Here

• They think a properly tightened bolt according to the standard tightening guideline will never loosen under any circumstances. It is not true as when the friction in the thread and under the head of the bolt starts to drop, it does not take a long

• They think it takes thousands of hours of vibration to loosen a bolt. It is not true as after side sliding starts, as few as 100 cycles are needed to loosen a bolt.

• They think fasteners take more torque to loosen than to tighten. It is not true as

• They agree with "I know it is tightened properly because I torqued it myself." It

There are various conventional fasteners available in the market, in this article, eight different frequently used fasteners are explained on how each one works and

Spring washer creates mechanical force against the nut and substrate surface which means mechanically "pushes the surface." What does this mechanical etching of the surfaces or how does this affect areas prone to corrosion? It may maintain the bolt tension in the beginning of assembly, but as time goes by, it loses its spring form and becomes flat due to the empty space between threads, and then, the bolt tension is reduced, and the assembly pressure is reduced, too, which results in the loosening of bolt and nut, and additional cost of spring washer is required (see

The star washer uses friction of the raised metal portions to mechanically "grip" the surface. This method allows an initial loosening as the washer rotates and grips into the substrate, and then bolt tension is already reduced, but it can prevent a further

in this chapter, some of their "truth" will be shared to see if they are true.

*DOI: http://dx.doi.org/10.5772/intechopen.85090*

50–75% of bolt proof load (see **Figure 2**) [1].

**4. Well-accepted myth**

time for a bolt to loosen.

it is easier to go downhill than uphill.

**5. Conventional thread locking fasteners**

is not true as it does not matter whoever tightens.

what is the area of improvement regarding performance and cost.

**Figure 2.** *Typical stress-strain curve of steel.*

*Liquid Thread Locking Solution for Machinery Assembly Industry DOI: http://dx.doi.org/10.5772/intechopen.85090*

Bolt tightening torque stretches bolt shank to at least 65% of its yield strength. Yield strength is the stress at which the bolt shank starts to stretch. If the stress is beyond this point, then the bolt shank will break. As shown in **Figure 2**, tightening torque elongates the bolt. Being an elastic material, elongated bolt wants to retract. That is when a bolt tension is generated and the spring force clamps parts together. Red marked area shows the max. clamp load. Typically, the acceptable clamp load is in the range of 50–75% of bolt proof load (see **Figure 2**) [1].
