**Bolts
It can also be manufactured from other materials other than iron and steel. In this respect, the bolts are classified in terms of their quality as breaking strength (tensile strength) and in case of lower yield stress or disproportionate elongation stress. Bolt quality classes are indicated as number of two digits, 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9. Exclusions from this two-digit display:
The first number multiplied by 100 gives the value of the tensile strength of the material.
If the second number is divided by 10 and multiplied by the tensile strength in step 1, the lower yield stress value up to quality 8.8 is obtained, after 8.8 the disproportionate extension stress value is obtained.
Tensile Strength: The maximum force per unit area a material can withstand.**

**Lower Yield Stress: In soft materials, a fluctuation occurs in the graph as it moves from the elastic deformation zone to the plastic deformation zone. The minimum point of this fluctuation is called lower yield stress.**

**Proportional Elongation Stress: Such a fluctuation does not occur in the transition from elastic deformation to plastic deformation in the graph of the hard material; the stress value corresponding to this transition point is called disproportionate elongation stress or yield stress.**

**Example-1: What is the tensile strength of a 8.8 bolt?
8x100 = 800 N / mm²
What is the tensile strength of a 12.9 quality bolt?
12x100 = 1200 N / mm²**

**Example-2: What is the lower yield stress value for 8.8 bolt?
8 / 10x800 = 640 N / mm²
What is the disproportionate strain value for a 12.9 bolt?
9 / 10x1200 = 1080 N / mm²**

**Example-3: What is the maximum force a 8.8 M12 bolt can withstand?
Tensile strength of 8.8 bolt was found to be 800 N / mm² in example-1. When the tensile strength is multiplied by the area of â€‹â€‹the circle, the desired force value is found.
800 N / mm² x π x R² / 4 = 800 N / mm² x π (12 mm) ² / 4 = 90.477.87 N = 90.48 kN **