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Fastener Identification

FASTENER IDENTIFICATION

 

The SAE bolt strength grades range from grade 2 to grade 8.  The higher the grade number, the greater the bolt strength.  Identification is determined by the line marks on the top of each bolt head.  The actual bolt strength grade corresponds to the number of line marks plus 2. The most commonly used metric bolt strength classes are 9.8 and 10.9.  The metric strength class identification number is imprinted on the head of the bolt. The higher the class number, the greater the bolt strength.  Some metric nuts are imprinted with a single-digit strength class on the nut face.

How to Determine Bolt Strength

 

MARK

CLASS

 

MARK

CLASS

Hexagon Head Bolt

4 --
5 --
6 --
7 --
8 --
9 --
10 --
11 --

4T
5T
6T
7T
8T
9T
10T
11T

Stud Bolt

4T


No Mark

4T

Hexagon flange bolt


w/ washer hexagon bolt


No Mark

4T

6T

Hexagon Head Bolt


Two Protruding

5T

Hexagon Flange Bolt

w/ washer hexagon bolt


Two Protruding

6T

Welded Bolt

4T

Hexagon Head Bolt


Three Protruding

7T

Hexagon Head Bolt


Four Protruding

8T

This page last updated: 16-Apr-2008

Content and Design © 2002-present WanderingTrail,  Ron Seegert
Common Sense and Safety should always be observed when working on your vehicle or doing modifications. Jackstands, wheel blocks, disconnecting the battery are a few of the basic safety precautions that should be used and may not be mentioned in the write ups on this site. You are responsible for your own installation, these write ups are a helpful guideline and should not be taken as an official installation instruction. My write up may be different from the kits currently out there, so alwasy double check the manufacturers installation instructions when installing anything. I try to keep the site up to date with changes that have occured as I discover them, but may not have the latest unless someone lets me know. If you feel that an install is above your capabilities after reading my write ups, I recommend getting together with a club and getting some help. Only a few times have I needed to employe some actual help from a shop to get something done. Usually welding or A/C work.
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