What do the marks on a bolt head mean?

The higher the grade, the stronger the bolt. English bolts have radial lines on their head to identify the grade, or strength class. The number of lines on the bolt head is 2 less than the actual grade. So, for example, a grade 5 bolt will only have 3 radial lines on its head.

What does grade 5 Mean on a bolt?

Grade 5 Bolts and fasteners are made of medium strength carbon steel and are specified under the Society of Automotive Engineers (SAE). If your application calls for heavier materials, you may need Grade 8 Bolts because they are the hardest and are often used in heavy manufacturing applications.

What do the numbers on top of bolts mean?

Bolt Grade Markings Each grade has a specific bolt strength. No matter the system used to grade the bolts, the higher number means the stronger the bolt. For most home and automotive applications, you won’t need anything more than a grade 8 bolt strength or metric class 10.9.

Is a Grade 5 bolt stronger than a Grade 8?

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.

How strong is a Grade 5 bolt?

120,000
Bolt Grade Markings and Strength Chart

Will Grade 5 bolts rust?

Many other grades exist but are used far less often. Grade 2, 5, and 8 are usually plated with a slightly blue-ish or yellow zinc coating, or are galvanized, to resist corrosion.

How many marks does a Grade 5 bolt have?

Many don’t realize, but when you need Grade 5 bolts, you are looking for medium strength carbon steel. Heat treated in a controlled atmosphere, these bolts can be identified by the three distinct marks located on the bolt head.

Whats stronger Grade 8 or Grade 5 bolt?

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.

What do letters on bolts mean?

The three-letter code is the manufacturer code (for example, HKT stands for Hau Kwang Enterprises) and the numbers (if metric) or radial lines (if SAE) refer to the bolts’ strength. If there are no numbers or lines present, assume the bolt is no better than a grade 2 (low strength).

What is the hardest bolt you can buy?

Commercial-grade 8 bolts are the strongest option available. They’re made from medium carbon alloy steel and have markings that include six raised dashes. The psi of the bolt is 150,000, meaning that it can withstand great deals of pressure because of the way it was quenched and tempered.

What are the grades for bolt head marking?

So there you have a quick overview of the major grades from SAE J429. As a quick summary: No marking = Grade 2. Three radial lines = Grade 5. Six radial lines = Grade 8. In Part 2 of our Head Marking Series, we talk about three additional standards that deal with inch-series fasteners, ASTM A307, ASTM A354, and ASTM A193.

What do head markings on fasteners tell you?

Fastener head markings usually accomplish two things: they identify the manufacturer of the fastener and the standard to which the fastener was made. We’ll talk about manufacturer head markings first, followed by fastener standards and how they govern the industry.

What does Wilson Garner grade 5 bolt head mean?

So as you can see, this bolt head has Wilson-Garner’s manufacturer mark and three radial lines. These lines indicate that the bolt is a Grade 5. Grade 5 fasteners have a minimum tensile strength of 120ksi for diameters ¼ inch through 1 inch and 105ksi for diameters over 1 inch through 1-1/2 inches.

What do the radial lines on a bolt head mean?

English bolts have radial lines on their head to identify the grade, or strength class. The number of lines on the bolt head is 2 less than the actual grade. So, for example, a grade 5 bolt will only have 3 radial lines on its head. A grade 8 bolt will have 6 radial lines on its head.