What is Material Grade in fasteners?

Posted by bolt_admin


Posted on December 5, 2017



Most people assume a bolt is a bolt, simply a chunk of metal that fastens things together. When in fact fasteners (nails, screws, bolts, etc.) are extremely complex mechanically-engineered hardware, made from different materials, with different thread and head types, shapes and sizes and grades. But what exactly does the material grade mean?

The easiest way to identify a grade is: the higher the number, the stronger it is. There are different types of strengths listed for each grade, such as proof strength, tensile strength, yield strength and shear strength

Here’s where it gets a little confusing: Grade 5 bolts have 3 radial lines on the head, Grade 8 bolts have 6 radial on the head and Grade 9 bolts have 9 radial lines on the head. As an average rule, Grade 5 fasteners have a tensile strength of approximately 120,000 lbs per square inch), Grade 8 fasteners have a tensile strength of approximately 150,000 lbs per square inch and Grade 9 fasteners have a tensile strength of approximately 180,000 lbs per square inch. The shear strength can then be calculated, as it is typically about 60% of the tension strength.

In order to determine toughness, you need to look closely at the hardness rating of the grades. The higher the ‘hardness’ number, the harder the material is, thus, its rating of toughness and resistance to damage.

It is important to note, no matter how much load your grade fastener can carry, if the material you are fastening isn’t strong enough to handle the loads too, your system will fail. Also, selecting the right material for your fastener will go hand-in-hand with its Grade rating, as some materials will be stronger than others in order to handle heavier loads.

If you’re looking for material grade fasteners, Bolt In has a vast range available. Our expert Gold Coast based team can answer all of your material Grade questions, and help to ensure you are selecting the correct fastener for the job.

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