Grade markings are identifying marks on a fastener that indicate the fasteners grade or strength specification.
Grade markings are important because they easily identify the grade, strength or sometimes both of the fastener for you as the packager or order puller as well as for the customer who installs the fastener.  This helps to ensure the proper fasteners are used in the proper applications. It is worth noting that not all fasteners have a grade marking.

Virtually all fasteners are made to a specification that dictates the chemical makeup of the material used to manufacture the part.  This ensures that all grade 5 bolts, for example, meet certain basic manufacturing requirements regardless of the manufacturer.  Grade markings can be found on both USS standard and metric Hex Cap Screws, Socket Cap Screws, Hex Nuts, and many other types of fasteners.

As you read on the previous section, there are many different types of fasteners and many different grades.  For now, we will focus on USS standard Hex Cap Screws and USS standard Hex Nuts and their markings.

These are the three types of markings you will see on Hex Cap Screws and Hex Nuts to determine it’s grade.  Later we will learn about different numbers and letters that you might also see on other types of hardware but these are the only markings, or symbols, that you see on USS standard nuts and bolts.

Grade 2

• The two images on the left are both Hex Cap Screws and the two images on the right are both Hex Nuts.  Both are viewed from the top looking down.  Grade 2 Hex Cap Screws will typically have no markings of any kind but you may also see 307A stamped on the head.

• The two images on the right are both Hex Nuts and again viewed from the top looking down onto the face of the nut.  Grade 2 Hex Nuts will have either no markings or may have some sort of marking. This is not a grade marking it is a manufacturers unique symbol.

 Grade 5

• The bolt head on the left has three “tick marks” or “dashes” on the top of the head identifying it as Grade 5.

• The Hex Nuts on the right show two different ways of marking the face of the nut as well as a side view showing one notch cut into each corner of the Hex Nut.  Notice that both nuts with markings on the face have two marks each and in both cases they are separated by a non marked corner or flat.

Grade 8

• The bolt head on the left has six “tick marks” or “dashes” on the top of the head identifying it as Grade 8.

• The Hex Nuts on the right again show two different ways of marking the face of the nut as well as a side view showing two notches cut into each corner.  Notice that both nuts with markings on the face have two marks each and in both cases they are on consecutive corners (could also be consecutive flats).