What is Grade A bolt?

Asked By: Kum Osante | Last Updated: 15th March, 2020
Category: sports climbing
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Bolts are made of different grades of steel. 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 SAE marking system uses raised dashes on the bolt head to indicate strength.

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Likewise, how strong is a Grade A bolt?

Bolt Grade Markings and Strength Chart

Head Marking Grade and Material Mechanical Properties
Min. Tensile Strength (psi)
3 Radial Lines Grade 5 Medium carbon steel, quenched and tempered 120,000
105,000
6 Radial Lines Grade 8 Medium carbon alloy steel, quenched and tempered 150,000

Similarly, what is ASTM a307 Grade A? ASTM A307 Grade A Covers the mechanical and material requirements for inch series fasteners in diameters from 1/4″ through 4″, made of carbon steel having a minimum tensile strength of 60,000 psi.

Then, is Grade 8 or 10.9 stronger?

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. A low carbon steel for general use.

What is the hardest bolt grade?

Grade 8 / Grade G 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.

39 Related Question Answers Found

What is the strongest bolt grade?

The strongest commercial-quality bolt is grade 8, marked by six raised dashes; its medium-carbon alloy steel has been quenched and tempered to achieve a tensile strength of 150,000 psi.

What does 12.9 on a bolt head mean?

The 12.9 is the Class head marking under ASTM F568M standard for Bolts of a high grade (1220 MPa), being Alloy steel, quenched and tempered. ASTM F568M is an ASTM International standard for metric bolts, screws and studs that are used in general engineering applications.

Are Grade 8 bolts brittle?

A Grade 8 has a very high tensile strength, but can be brittle. In applications such as suspensions, a very high number of load/unload cycles can produce work hardening, which produces an immediate, or catastrophic failure.

Is grade C the same as Grade 8?

Grade C. Grade C is a thru-hardened medium carbon zinc plated alloy steel. No head markings (manufacturers mark may also be included). Finish is equivalent in strength to Grade 8 but without the yellow color.

What does 8.8 mean on a bolt head?


If you have ever looked a metric hex bolt you might notice the markings 8.8, 10.9 or 12.9 this does not mean grade 8,10 or 12. The grade 8.8 refers to the tensile strength which is generally 116,000 psi, grade 10.9 is generally 150,000 and grade 12.9 is generally 175,000 psi.

Is 8.8 high tensile?

Grade 8.8 high tensile steel is often referred to as the structural grade for bolts. It is the most common form of high tensile material and is usually stocked in plain finish or zinc.

Will Grade 8 bolts rust?

According to K-T Bolt Manufacturing Inc., Grade 8 bolts "are used in demanding applications such as automotive suspensions. Grade 8 bolts have 6 evenly spaced radial lines on the head." Unlike stainless steel, which is highly resistant to corrosion, steel, however reinforced, will oxidize over time and rust.

What are the different types of bolts?

Types of bolts
  • 3.1 Anchor bolt.
  • 3.2 Carriage bolt.
  • 3.3 Elevator bolt.
  • 3.4 Flange bolt.
  • 3.5 Hanger bolt.
  • 3.6 Hexagon bolt/Tap bolt.
  • 3.7 Lag bolt.
  • 3.8 Machine bolt.

What do the letters on a bolt head mean?

What do they mean? The lines on the head of a bolt indicate its grade. SAE J429 (Society of Automotive Engineers) bolts have radial lines, whereas ASTM (American Society for Testing and Materials) uses a combination of letters and numbers to indicate the grade.

Is there a grade 10 bolt?


There's no such thing as a grade 10. There's a 10.9 in metric. From the course I sat thru a couple months back grade 8 is the strongest bolt grade for SAE sizes.

How strong is a grade 8.8 bolt?

Usually a tensile strength in the range of 112,000 to 116,000 PSI. In the metric world (a.k.a. ISO) the most common bolts are marked with an 8.8, 10.9, or 12.9. If there are no head markings at all, they are most likely comparable to the SAE grade 2. The 8.8 is comparable to the SAE Grade 5.

Is a Grade 8 bolt stronger than stainless steel?

Stainless steel bolts are rated for corrosion resistance. 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 material is a Grade 8 bolt made of?

From the internet: Grade 8 bolts are comprised of carbon alloy steel, thus giving them a high psi rating. Zinc or yellow zinc grade 8 bolts are available to resist corrosion. The factor that makes a grade 8 bolt different from a lower grade bolt is its preload strength.

What is tensile strength of a bolt?

What Is the Tensile Strength of Grade 8 Bolts? The tensile strength of a grade 8 bolt is 150,000 pounds per square inch. Tensile strength is the maximum load in tension (stretching) that a part can carry without breaking.

What is a Class 8.8 metric bolt?


Grade 8.8 Bolts are manufactured using medium carbon steel that has been quenched and tempered. Used in railroad equipment, motors, engines and processing equipment, grade 8.8 bolts exhibit good tensile strength and perform well in most environments.

How strong is a 10.9 bolt?

Used in automotive applications and for bolting large and forged parts, metric 10.9 bolts exhibit high tensile strength and good wear resistance. Our metric grade 10.9 bolts meet ASTM A324 grade BD and SAE J429, grade 8 standards. The yield strength of the bolts is 940 and the tensile strength is 1040 MPa.