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Grade Markings In General
Head markings on cap screws are your assurance that the fastener you
choose will do the job it's designed to do.
The Society of Automotive Engineers and the Industrial Fasteners Institute
have established specific ranges of hardness and tensile strength for each
grade of fastener.
There are certain applications which engineers have determined are
appropriate for the various grade of fasteners. Observe
the grade markings to be sure the bolt or cap screw you select will meet
the
requirements of your job.
Grade 2 Fasteners
Often referred to as "hardware" quality, these fasteners are typically
made of low-carbon steel. They are ideally suited for holding wood pieces
together (in combination with appropriate nuts and washers) or general
hardware use where higher strength is not required.
There is no grade marking on the head of Grade 2 fasteners, although
many manufacturers will put a distinguishing company identification on the
head. |
Grade 5 Fasteners
Grade 5 fasteners are made of medium-carbon steel. These fasteners are
then quenched and tempered for the additional strength necessary for most
automotive uses and other applications where strength is a moderate
concern.
The grade marking on the head of a Grade 5 fastener is three
equally-spaced lines coming out from the center of the head.
Manufacturers` identifications are added for traceability.
Grade 8 Fasteners
Grade 8 fasteners are manufactured of medium-carbon alloy steel for the
most demanding applications. These fasteners are then quenched and
tempered to superior strength and hardness qualities.
The grade marking on a Grade 8 fastener is six equally spaced lines coming
out from the center of the head. Once again, the manufacturer's mark is
necessary for traceability.
Do not confuse the use of Grade 8.2 boron bolts with true Grade 8
fasteners. The two grades have different characteristics and should not be
used interchangeably.
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