Fundamentals of Threaded Fasteners and Bolting Brochure

Distance Learning Course: Fundamentals of Threaded Fasteners and Bolting

Bolt Science has developed a distance learning course on the Fundamentals of Threaded Fasteners and Bolting.

This online training course on the fundamentals of threaded fasteners and bolting seeks to provide the background knowledge to allow problems to be identified and the likely root cause established. It also identifies what constitutes best practice.

The training covers an introduction to fastener threads, strength of bolts and why they should normally be tightened. Failure modes of fasteners and their identification is covered, such as self-loosening, fatigue, and thread stripping. Torque tightening, bolt preload and the practices used to check the tightness of bolts are presented. This training does not include any calculations. Another course offered by Bolt Science covers this aspect (the Bolting Technology for Engineers and Designers online course).

View the Brochure:Fundamentals of Threaded Fasteners and Bolting.

Background Torque tightening of a bolt

Many Engineers require a working knowledge of threads and fasteners without having the need to complete any calculations. This training course is intended for such Engineers. Practically every engineering product with any degree of complexity uses threaded fasteners. Although threaded fasteners are generally considered a mature technology, significant problems exist with their use. Incorrect selection and tightening of a fastener can result in loosening, fatigue, and thread stripping issues, amongst others, that can have serious implications for a joint's structural integrity. Such joint failures are widespread across many industries and often involve material loss and sometimes fatalities. This online distance learning course presents key knowledge and facts to an Engineer on threaded fasteners and bolting issues likely to arise on a day to day basis.

This online distance learning course is designed for:

Bent bolt Technicians
Field Engineers
Maintenance Staff
Project Leaders.
Engineering Supervisors
Engineering Managers

There is narration provided with the course. This can be turned off if not required. There are several optional quizzes included on the course that allows you to assess how much of the material you have absorbed. There is also a final quiz that contains questions on all the course material. A course completion certificate is available once you have completed all the modules, including the quizzes.

Key benefits of this training

This online distance learning course will help you to
1. Understand the terminology used for threaded fasteners and bolting.
2. Understand the common modes of failures of fasteners and the possible reasons why that type of failure occurred.
3. Understand the differences between coarse and fine threads and the tolerancing of threads.
4. Understand the essential material properties of a bolt and how their strength is defined.
5. Understand the fundamental reasons why bolts are needed to be tightened.
6. Understand what is meant by joint separation or joint decompression and how to prevent it from occurring.
7. Understand torque tightening, the factors that affect the tightening torque and the scatter that is involved in the process.
8. Understand what is torque auditing, the different approaches involved and the potential issues involved.
9. Understand the causes of nuts and bolts coming loose, the effectiveness of different locking methods and how loosening can be prevented.

Course Documentation

A training course handbook is provided as part of the training that can be viewed online and printed out, if required. The handbook contains background information to the material presented on the course.

Course Agenda and Contents

Introduction to Threaded Fasteners

Some thread terminology.
Background to modern threads - Whitworth, Sellers and metric threads.
Fine and coarse thread and the advantages/disadvantages of each.
The basic profile of Unified and metric thread forms.
Thread tolerance positions and grades and tolerance classes.
The stress area, what it is and how is it derived.

Strength of bolts

The principles of bolt elongation, bolt stress and load.
Yield, tensile strength and proof load properties.
Details of common bolting specifications.
Upper and lower strength limits for bolts.
Bolt and nut head markings and identification of correct components.
Stainless steel fasteners ISO 3506, Duplex and Super Duplex.
Nut/bolt combinations, nut strength versus bolt strength.

Photo of a fatigue failure of a bolt

Fastener Failure Modes

Overview of the ways threaded fasteners can fail.
Manufacturing Related Quality Defects.
Design Related Quality Defects.
Failure by insufficient preload.
Fatigue failure of bolts.
Thread Stripping Failures - internal and external threads.
Bolt overload from applied forces.
Bearing stress under the bolt head or nut face.

Why bolts should be tightened

Why is tightening a bolt important?
How a preloaded joint sustains an axial load.
Joint separation – what is it and why is it important.
Why tightening bolts is important for shear loaded joints.
Explanation of why the bolt sustains a small proportion of an axial load.
Bolt stretch and joint compression.

Torque Control

What is meant by a tightening torque. Units used to measure torque.
Torque and bolt preload.
How torque is absorbed by a nut/bolt assembly.
The torque-tension graph.
The relationship between the tightening torque and bolt preload.
The factors which affect the torque-tension relationship.
Determining the correct tightening torque.
How to determine the appropriate tightening torque.
Tightening of the bolt head or the nut.
Scatter in the bolt preload resulting from friction variations.
Prevailing torque fasteners and how it affects the overall torque value.
Placing upper and lower limits on the torque value.
Effect on the tightening torque of flange head and countersunk fasteners.

Fundamentals of Torque Auditing

Why and when is torque auditing required?
What is meant by torque auditing?
What is meant by the terms, residual and break loose torque?
Why is the tightening torque less than the loosening torque?
The difference between torque and fastener preload.
The different torque auditing methods
The residual torque or on-torque method
The Breakloose or Off-Torque Method
The Marked Fastener Method.
The Static Audit Torque Quality Check and why it can be useful.
Issues with Torque Auditing: Joint Relaxation and Changes in the Friction Value.
Witness or Stripe Marking of Fasteners.
Why check the tightness of a bolt or nut on an assembly in service?

Photo of a helical spring washer

Self-Loosening of Threaded Fasteners

Explanation of the two main types of loosening process, relaxation and self-loosening.
The torque that is driving the loosening process.
Junker's Theory of Self-Loosening of Fasteners.
Why do Threaded Fasteners Self-Loosen?
The Junker Vibration Test Machine.
Video describing a Junker test to assess the performance of a fastener to resist self-loosening.
Loosening Curve for a Non-Locked Hexagon Headed Bolt or Nut
Loosening Curve for a Helical Spring Lock Washer.
Loosening curves for Internal and External Serrated Tooth Washers.
Loosening curves for Nylon Insert Nuts and the Wedge Lock Type of Washer.
The effectiveness of wire locking and tab washers to prevent self-loosening.
Potential fatigue failure implications of using a locking device.
What mechanism causes fasteners to become detached once loose.
Conclusions from the research and how loosening can be prevented.

Included in the training are case studies. These case studies are drawn from various industry sectors. Catastrophic accidents have occurred as a result of the failure of bolted joints, they illustrate what can go wrong when bolted joints fail and what lessons can be learned. There is a course handbook provided as part of the training that can be viewed online and downloaded and printed.

Course Duration

The course represents between 5 to 8 hours of study (some people would complete in a shorter time, others longer depending upon their previous experience and knowledge). Access to the course will be available for three months following the login and password details being provided.

Course Director Fatigue failure of a bolt

Dr Bill Eccles is a mechanical engineer with 40 years experience in mechanical engineering with the last 20+ years specialising in bolted joint technology and analysis. He is a Chartered Engineer and a Fellow of the Institution of Mechanical Engineers and has a Doctorate in Engineering on the self-loosening of threaded fasteners.

Bill has written several articles on bolting technology and has developed bolted joint analysis software that is used by major organisations around the world.


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