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Blessed Bolts or Freaking Fasteners Or Bolt Basics!

by Michael Lippig

Bolts and screws are not something that occupies a lot of our reliability thoughts. After, the life of an appropriate bolt in a non-aggressive environment has been extrapolated to something like 11,000 years. Yet if you use the wrong fastener, it is bound to be very aggravating. It may not even survive its own virgin installation!

Luckily, there are some visual cues to help guide against using the wrong fastener. The following table shows grading of common US and Metric fasteners.

Maybe one day we will only have just the same system and less confusion. But you know the saying; “US is changing to the Metric standard inch by inch.” 

US Bolts (SAE J429)

Marking

Grade

Sizes

Load (psi)*

Strength (psi)**

image001

Grade 2

¼” -3/4”

55,000

74,000

+3/4” – 1 ½”

33,000

60,000

Grade 5

¼” – 1”

85,000

120,000

+1” – 1 ½”

74,000

105,000

clip_image004_0003.gif

Grade 8

¼” – 1 ½”

120,000

150,000

Metric Bolts (ISO R898)

Marking

Grade

Sizes

Load (psi)*

Strength (psi)**

clip_image001_0000.gif

Class 4.6/ Class 5.8

1- 35mm

33,000/ 55,000

60,000/
74,000

image005.gif

Class 8.8

Up to 16mm

84,000

116,000

16 – 72mm

87,000

120,000

image006_0002.gif

Class 10.9

5 – 100mm

120,000

150,000

image001_0001.gif

Class 12.9

1.6 – 100mm

141,000

177,000

*Load= Minimum load bolt must handle without permanent deformation.
**Strength (tensile)= Minimum load bolt must handle before braking or fracturing.