Thursday, June 11, 2009

Bolt Strength Calculator | Bolt preload calculation

Bolt nomenclature:

In almost all Engineering Field, usage of bolt has made significant impact. In simple words, every Design Engineer should know the steps involved in bolt application and "How to Design a Bolt".

Bolt Terms & Definition

As you might have come across, there are different types of bolt available in the market either in inches or metric. Some of the familiar ones are Hex bolt,Eye bolt,U bolt,anchor bolt etc. Watch out for bolt/fastener type chart.

Each type of bolt has specific purpose. In this session, I would like to show you calculations involved in designing a bolt.

Based on this idea, we will see two sites one is about Bolt strength calculation software and other one about Bolt pre-load design.

Bolt Strength Calculator (software):

This software check for bolt failure under various load conditions. And helps you to select proper bolt.


  • Torque
  • Clamping force
  • Estimated breaking strength
  • Estimated yield strength
  • Convert between US and Metric units
  • Bolt strength charts
  • Bolt torque chart standard
  • Screw strength charts
  • Thread tensile stress area
  • Breaking strength
  • Torque
  • Nut strength
  • Thread strength
  • Endurance Strength ( fatigue strength)
  • Spring Constant
  • Prying forces
  • Corrosion Resistant Materials
  • Hardness to strength charts
  • Nut K factor - effect of phosphate coating on bolt torque
  • Grade 8 bolt torque value
  • AN bolt torque settings
  • Bolt torque specification guide
  • Stainless steel bolt torque specifications

Bolt Strength calculator

Fig: Bolt Strength calculator

This you can get from mechanic toolbox. This is not available for free, you can get it by paying 40$.. Purchase now.

Bolt Strength and preload design:

This site would help you to understand bolt specifications, how to read thread specifications/callout.

eg: 1/2-13UNC-2

which means:

  • 1/2 bolt diameter
  • 13 threads per inch
  • UNC thread type
  • 2 fit class

There are four Fit Classes, ranging from falling-off-loose to scientific-instrument-tight.

  • Class 1 = Loose
  • Class 2 = Free
  • Class 3 = Medium
  • Class 4 = Close

The last but not the least you can learn about how to select bolt based on strength chart and how to calculate preload for a bolt.

Also take a look at Bolt Grade Markings and Strength Chart,Bolt Ultimate Strength Calculator