An OEM ISO standard Bolt is a type of bolt used in automotive applications. It is designed for strength and durability and has certain properties. The most common strength classes are 8, 10.9, and 12.9. Other strength classes exist, but are less common. A bolt's strength class is represented by a number before a decimal, which refers to its ultimate tensile strength (uts). Uts is defined as the ultimate tensile force per unit area, and is measured in megapascals (MPa) divided by 100. Thus, a bolt with an 8.8 strength class is equivalent to a SAE Grade 5 bolt.
An ISO-standard metric bolt has three dimensions: the overall length, the nominal diameter, and the thread pitch. The first two dimensions are in millimeters, while the third is a number indicating the distance between the peaks of adjacent threads. Lower numbers are finer and higher numbers indicate coarser threads. A bolt's hex head is determined by its diameter, while twelve-point heads are only used on special fasteners.
Stainless steel bolts are generally a high-quality option, as they are resistant to corrosion. However, they are not the strongest option, and their tensile strength is not very high. A2-70 bolts are typically made of steel grades A2 and A4 class 70. Their tensile strength is approximately 700 Mpa. Generally, the A2 version of a bolt's strength is made of Stainless Steel grade 304, which is known for its corrosion-resistant properties.