Grade Markings Help You Choose the Right Fastener for Your Project
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. All Elco fasteners meet or exceed
There are certain applications which engineers have determined are
appropriate for the various grade of fasteners. Do-it-yourselfers
can use the grade markings to be sure the bolt or cap screw will meet
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
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
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.