What do the letters on the head of a bolt mean?

You can usually figure out the grade, or strength, of a bolt by looking at the markings on its head. English bolts (U.S.S. or S.A.E) are categorized by grade, from grade 2 to grade 8, where the grade represents inch strength. The higher the grade, the stronger the bolt.

What is the number on a bolt head?

In addition, most metric bolts are identified by a number stamped on the bolt head, such as 4.6, 5.8 or 10.9. The number has nothing to do with the size, but does indicate the relative strength of the bolt. The higher the number, the stronger the bolt.

What does 8.8 mean on the head of a bolt?

The two figures indicate the tensile and yield strengths of the bolt or screw. In the case of a 8.8 grade bolt the first figure signifies that the Tensile Strength is at least 800MPa. The second figure signifies that the fastener will begin to yield at 80% of the Ultimate Tensile Strength, i.e. at least 640MPa.

What does 6 markings on a bolt head mean?

SAE grade 8
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. Three radial lines will indicate an SAE grade 5 fastener, while six radial lines will indicate an SAE grade 8 fastener.

What does 7 on a bolt head mean?

Head Mark “7”: 8.8. Head Mark “8”: 9.8.

What do the numbers 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.

What does the grade marking on a bolt head mean?

Our second example, Figure 3, will actually have a grade marking: 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.

What are the standard bolt identifications?

STANDARD BOLT IDENTIFICATION MARKINGS Proof Load (psi) Yield Strength Min (psi) Tensile Strength Min (psi) Low‐ or Medium‐ Carbon Steel 1/4 THRU 1 ½ 33,000 36,000 Low‐Carbon Steel 1⁄4  thru 4 −− −− SAE J429 Grade 2 Low‐ or Medium‐ Carbon Steel 1⁄4  thru 3⁄4 Over 3⁄4  thru 1 ½ 55,000 33,000 57,000 36,000 74,000 60,000  No Grade Mark

What are the different grades of bolts?

English bolts (U.S.S. or S.A.E) are categorized by grade, from grade 2 to grade 8, where the grade represents inch strength. 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.