Blessed Bolts or Freaking Fasteners Or Bolt Basics!

Share on linkedin
Share on twitter
Share on facebook
Share on email

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/
image005.gif Class 8.8 Up to 16mm 84,000 116,000
16 – 72mm


image006_0002.gif Class 10.9 5 – 100mm 120,000 150,000
image001_0001.gif Class 12.9 1.6 – 100mm



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

At IDCON, we understand the pressure you face trying to build a reliable plant.
We provide side-by-side reliability and maintenance consulting and training designed to keep your equipment running.

For over 45 years, we’ve partnered with 100s of manufacturing plants around the world to eliminate the costs and the pressure caused by unreliable equipment. And we’d love to do the same for you.

Contact us today to see how we can help you keep your plant running.

Related Articles

Smart Methods in Maintenance: Part 2

Most maintenance problems are the result of neglecting the very basics of essential component care and inspections, including improper lubrication, poor operating practices, faulty alignment and balancing, and lack of

Read More »
Michael Lippig

Michael Lippig

Senior Consultant - IDCON, Inc.

Want weekly Reliability & Maintenance Tips?

Best practices. Common sense. Pratical tips.
All designed to help you and your team keep your plant running

IDCON © 2020 All rights reserved

Free Download & Video

8 Steps to Successfully Implement Preventive Maintenance

Reduce your costs with an effective PM program