Many of our bolt styles are available in various grade and class options with each grade containing distinctive head markings. The following markings are the primary indicators used on our parts.

Standard Parts

Grade of Material

Marking

Appearance

Nominal Size Range

Proof Load
(PSI)

Yield Strength
(Min. PSI)

Tensile Strength
(Min. PSI)

Grade 2

No Marking

1/4" - 3/4"

3/4" - 1 1/2"

55,000

33,000

57,000

36,000

74,000

60,000

Grade 5

3 Radial Lines

1/4" - 1"

1" - 1 1/2"

85,000

74,000

92,000

81,000

120,000

105,000

Grade 8

6 Radial Lines

1/4" - 1 1/2"

120,000

130,000

150,000

18-8 & 316 Stainless

No Standard Marking

Up to 1"

45,000
minimum

85,000
minimum

A325 Structural Bolts

A325

1/2" - 1"

1 1/8" - 1 1/2"

85,000

74,000

92,000

81,000

120,000

105,000

Metric Parts

Class of Material

Marking

Appearance

Nominal Size Range

Proof Load
(MPA*/PSI)

Yield Strength
(MPA*/PSI)

Tensile Strength
(MPA*/PSI)

Class 8.8

8.8

<16mm

16mm - 72mm

580 / 84,100

600 / 87,000

640 / 92,800

660 / 95,700

800 / 116,000

830 / 120,000

Class 10.9

10.9

5mm - 100mm

830 / 120,350

940 / 136,300

1040 / 150,800

*MPA = Megapascal. 1 MPA = 145 PSI (pounds per square inch)



Proof Load - The amount of tensile (pull apart) stress that a bolt must be able to withstand without permanent deformation.

Yield Strength - The amount of tensile stress at which a specific permanent deformation will take place.

Tensile Strength - The maximum amount of tensile stress that can take place before a bolt breaks or fractures.


Fastener SuperStore carries these grade options in the following standard categories:

Fastener SuperStore carries these grade options in the following metric categories: