What do the symbols on top of bolts mean?

What do the symbols on top of bolts mean?

You can usually figure out the grade, or strength, of a bolt by looking at the markings on its head. English bolts (U.S.S. or S.A.E) are categorized by grade, from grade 2 to grade 8, where the grade represents inch strength. The higher the grade, the stronger the bolt.

What do the marks on bolt heads mean?

The markings can identify the standard to which the bolt was made. For instance, if a bolt head contains three radial lines, then it’s a Grade 5 bolt. If it contains five radial lines, then the bolt is Grade 8.

What are bolt grade markings?

The grade of a bolt determines the maximum amount of stress (tensile strength) that the bolt can handle. Tensile strength is the amount of pull the bolt can withstand before breaking. The method used for tightening the bolt is also dependent upon the grade of the bolt.

How can you tell if a bolt is a Grade 5?

Grade 5 bolts are case hardened, meaning the bolt has been heated enough to hardened the outside of the bolt but not enough to harden the inside portion. Grade 5 bolts are identified by 3 evenly spaced radial lines on the head.

How do you read a nomenclature bolt?

Look at the first number to find the screw’s diameter. It corresponds to the width of the threads on the screw’s shaft. In the metric system, the diameter is always measured in millimeters. For instance, on a M12 x 1.75 x 85 callout, M12 is the diameter. It means the external threads are 12 mm (0.47 in) wide.

Are grade 12.9 bolts brittle?

10.9 and 12.9-grade hardened bolts, nuts and studs become fragile due to thinning out. They also cause great harm to the environment and employees. They cause wounds in the respiratory tract and in the lungs of those who inhale the steam.

What’s the difference between a Grade 5 and a Grade 8 bolt?

Grade 8 bolts have been hardened more than grade 5 bolts. Thus they are stronger and are used in demanding applications such as automotive suspensions. Grade 8 bolts have 6 evenly spaced radial lines on the head. Grade G is roughly equivalent to Grade 8.

How are bolts specified?

A bolt’s size is classified based on a number of dimensions, namely the bolt’s diameter, length of shank, thread pitch, grade, thread length and head size. Bolts can me specified in metric using millimeters, but the standard, internationally-recognized descriptions of bolt sizes are in inches.