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What is Grade A bolt?

4 min read

Asked by: Heather Anderson

Systems of Bolt Grades 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 strong is a Grade A bolt?

Grades of Bolts – Bolt Grade Markings & Bolt Strength Chart

Bolt Grade Markings & Strength Chart – Metric Steel Bolts
Head Marking Grade/Specification Tensile Strength min (MPa)
Class 10.9 1040 (150,000 psi)
Class 12.9 1220 (176,000 psi)
Usually stamped A-2 or A-4 A2 & A4 Stainless 500 Min 700 Typical

How do you tell if a bolt is grade A?

You always want to see 3 radial slashes on the top of the head that mark is a grade.

Is it Grade 8 or Grade A bolts?

Grade 8 – Grade 8 bolts are made from medium carbon alloy steel. The bolts of this grade feature 6 radial lines. The nominal size of the grade 8 bolts can be from 1/4″ to 1 1/2″. The minimum yield strength of this grade bolt is 130,000 psi.

What is the difference between class and grade bolts?

The first system is referred to as grades of fasteners, which uses imperial measurements, i.e. inches. They are primarily used in North America where the imperial system is still in common use. The second system is called classes of fasteners, which uses metric dimensions, i.e. millimetres (mm).

What grade bolt is strongest?

Grade 9 Bolts

Grade 9 structural bolts, also known as grade 9 hex cap screws, are one the strongest structural bolts that can be used today. While the typical grade 8 bolt has a tensile strength of 150,000 PSI, a grade 9 bolt has a tensile strength of 180,000PSI.

What is the hardest grade bolt?

Grade 8

Grade 8 is the hardest, Grade 5 is medium, and Grade 2 is the softest. This is the most common grade of steel fastener and is the least expensive. Grade 2 bolts have no head marking, although sometimes a manufacturer’s mark is present. This grade of bolt is made from low or medium carbon steel.

How do I choose a bolt grade?

If an inch base bolt has three hash marks on its head it's a grade five. These have a minimum tensile strength of 120,000 psi from one quarter to one inch in diameter.

Do stainless steel bolts have a grade?

303 and 304 Stainless are the most commonly listed grades, the standard grade for stainless fasteners. They are corrosion-resistant and durable. They are often used in marine applications in freshwater environments but will not work as effectively in a salt-water environment as 316 stainless.

What is the strongest stainless steel bolt?

BUMAX® Ultra

BUMAX® Ultra has proven itself as the world’s strongest bolt – in various highly-demanding critical fastener applications around the world where standard fasteners are simply inadequate.

What are Grade C nuts?

C. This nut grade denotation is for nuts that are used in heavy construction. They are marked with three curved lines around the central hole. This grade meets ASTM A563 specifications and is commonly used with ASTM A325 and ASTM A354 bolts.

Are stainless steel bolts stronger than Grade 8?

Stainless Steel Grades & Strength

Bolt strength is rated in PSI (pounds per square inch). A stainless steel bolt has the same PSI rating as a grade 5 bolt (125,000 PSI). A grade 8 bolt has a stronger rating with a PSI of 150,000.

What is the strongest metric bolt?

Metric Grade 12.9 Hex Cap Screws

Used in high stress environments, grade 12.9 fasteners are the highest class of metric cap screws. Where Grade 8 fasteners have a 150,000 psi tensile strength, 12.9 fasteners have a 180,000 psi tensile strength, making them more durable than the grade 5.

Are titanium bolts stronger than steel?

The strength and low weight of Titanium make it exceptionally unique, and some grades of Titanium can be anywhere from two to four times stronger than Stainless Steel. These features make Titanium ideal in some aerospace, medical and military applications.

What does 9.8 mean on a bolt?

Higher Number Means Stronger

The higher the ISO numbers are, the stronger the bolt. A metric bolt designated as ISO class 6.8 roughly corresponds in strength to an SAE Grade 2 bolt. Bolts of ISO class 8.8 and the slightly stronger class 9.8 roughly correspond to an SAE Grade 5 bolt.