6th December 2019


Is a 10.9 Bolt stronger than Grade 8?

Also known as A-2 stainless, 18-8 is the most common grade of stainless steel for general use. A tempered medium carbon steel. Class 10.9 is stronger than class 8.8, and is commonly found in high strength automotive applications. Class 10.9 is similar to grade 8.

Keeping this in consideration, how many marks are on a Grade 8 bolt?

Bolt Grade Markings and Strength Chart
Head MarkingGrade and MaterialMechanical Properties
Min. Tensile Strength (psi)
3 Radial LinesGrade 5 Medium carbon steel, quenched and tempered120,000
6 Radial LinesGrade 8 Medium carbon alloy steel, quenched and tempered150,000

What is the hardness of a Grade 8 bolt?

Materials - Medium Carbon Steel Bolts in SAE J429 (Grades 2, 5 and 8)
GradeNominal size, inchesCore hardness, Rockwell
2¾ - 11/2 inchB70 to B100
5¼ - 1 inchC25 to C34
1 - 1-1/2 inchesC19 to C30
8¼ - 1-1/2 inchesC33 to C39
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