Bolt Grade Markings and Strength Chart
|Grade and Material||Nominal Size Range (inches)|
|Class 8.8 Medium carbon steel, quenched and tempered||16mm - 72mm|
|Class 10.9 Alloy steel, quenched and tempered||5mm - 100mm|
|Class 12.9 Alloy steel, quenched and tempered||1.6mm - 100mm|
Similarly, what is a 8.8 Bolt?
The first digit relates to the ultimate strength of the material, whilst the second is the ratio of yield stress to ultimate strength. Thus grade 4.6 bolts have an ultimate material strength of 400N/mm2 and the uield (or proof) stress is 60% of the ultimate strength.
What is a metric bolt?
The size of a metric screw or bolt is specified as diameter, pitch and length, in millimeters (millimeters is abbreviated "mm"). If you need to know the threads per inch of a metric fastener, first convert pitch from millimeters to inches (multiply by 0.03937), then divide 1 by that number.
What does 12.9 mean on a bolt?
12.9 grade steel means that a component manufactured form this grade of steel has 12X100 N/mm^2 tensile strength and 9 is a multiplier means 90% of 1200 = 1080 N/mm^2 is the yield strength of the grade. Similarly we also have grade 8.8 , 10.9 , 6.8 also.