Understanding the Different Markings on Fasteners

By Alana Hromidko • 03.01.22

Why do Fasteners have Markings? 

When shopping for fasteners, you may have noticed the head of fasteners have markings engraved. These markings have a specific purpose that will help you understand the fastener more in-depth. The markings are an indication of the fastener's make, material, and dimension.

The tool manufacturer engraves these markers as a helpful way for customers to be aware of what they are using or purchasing. Each manufacturer is required to engrave a unique marker that is specific to their brand. The brand marker is especially helpful as it allows you to trace the fastener back to the manufacturer if there is a defect.

Common Markings on Nuts and Bolts

When it comes to nuts and bolts, there are many markings that you may come across. Common markers include letters, numbers, dashes, slashes, dots, and many more. Many nuts and bolts follow SAE or Metric standards ensuring strength and reliability. 

SAE vs. Metric Markings

SAE Markings

The Society of Automotive Engineers created a system of classes or grades to identify valuable information about the fastener. The grade of a fastener can represent what material it is made out of, its hardness range, and its strength characteristics.

The SAE J429 standard has specific requirements for bolts, screws, studs, sems, and U-bolts up to 1-1/2" in diameter. Fasteners meeting SAE J429 standards have radial lines engraved on the bolt head. Grade 2, 5, and 8 are the most common grades of fasteners from the Society of Automotive Engineers. The higher the grade is, the stronger the material that makes up the fastener.

SAE Grade 2 

  • Does not have any radial line markings

  • Lowest SAE grade with the least strength

  • Compromised of low or medium carbon steel

SAE Grade 5 

  • Have three radial lines engraved

  • Medium level strength

  • Compromised of medium quenched and tempered carbon steel

SAE Grade 8

  • Has six radial lines engraved

  • Highest SAE grade with the most strength

  • Compromised of medium quenched and tempered carbon alloy steel

Metric Markings

Metric grades are set by the ISO (International Standards Organization). Metric markings combine two numbers separated by a dot. The number markings are engraved or stamped on the top or side of the bolt head. The common grades for metric are 5.8, 8.8, 10.9, and 12.9. The higher the numbers are, the stronger the material of the fastener is. 

The number that appears before the decimal, when multiplied by 100, will provide the approximate minimum tensile strength of the bolt. The number after the decimal, when multiplied by 10, will provide the approximate yield strength percentage in relation to the minimum tensile strength. 

Markings on Screws

Many screws have consistent markings that make it easy to distinguish the size of the screw. With Conquest concrete screws, for example, the length in decimal form is stamped on the head of the screw. Additionally, the Conquest concrete screws include a shield symbol stamped on the head of the screw that represents the Conquest brand. 

Conquest Concrete Screw

Markings on Wedge Anchors

The markings for concrete wedge anchors are different from screws. Wedge anchors have a letter marked on the head of the anchor. The letter signifies the specific length of the anchor. Check out the spec sheet for the Conquest wedge anchors to see what the letters equate to in length sizes. Conquest wedge anchors also have a Conquest shield stamped on the clip at the bottom of the fastener.

Conquest Concrete Anchor

Find it Fast. Get it Fast. 

Fasteners Plus carries a variety of screws, connectors, anchors, nails, power tools, and more! Place your orders at FastenersPlus.com and our dedicated team will get quality products sent to you. If you have any questions about fastener options, please do not hesitate to reach out to our Product Experts at (888) 794-1590 or by email at customerservice@fastenersplus.com.


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