Bolting Technology Brochure

Bolting Technology

This course is an introduction to bolting technology and includes key information on the subject. A brochure is available on this course and can be downloaded by clicking on the link below.

Brochure on the Course on Bolting Technology

This training has been delivered world-wide and receives very positive feedback:

"This course provided an exceptional insight into bolting technology. It covered a thorough range of topics from fastener design first principles to failure analysis. From an engineer's perspective it is an excellent course delivering a unique insight into a subject that is an often misinterpreted basic engineering fundamental. The engineers who attended from BAE Systems found the course extremely valuable, gained a great deal of knowledge over the 2 days and ranked it as a superb, informative course."

Andy Lovatt, Mechanical Design Engineer, BAE Systems Land (UK)

The course content includes:

Introduction to Threaded Fasteners

  • Know the meaning of thread terminology.
  • Learn when it is appropriate to use a fine rather than a coarse thread.
  • Be aware of the principal bolt and nut strength property classes and how they should be specified.
  • How to match the nut strength to that of the bolt so that thread stripping problems are prevented.
  • Find out why bolt tensile fracture is preferable to the threads stripping.
  • Learn what the proof load is and why it is used.
  • Be able to identify the meaning of the markings on bolt heads and nuts.
  • Learn about the thread stress area and how it is derived and used.
  • Be able to calculate the tensile strength of a threaded fastener.
  • Understand how a pre-tensioned bolted joint sustains an applied load.
Fatigue failure photo of a bolt Preload Variation in Threaded Fasteners
  • Learn why there can be such a significant variation in the preload (tension in the bolt) and the consequences of this.
  • How the torque is distributed between the threads and the nut face when free spinning and torque prevailing fasteners are used.
  • Why preload is so crucial in a bolted joint.
  • How preload variation can be accounted for at the design stage.
  • The effect of the tightening method on the preload variation sustained by a fastener.
Galling of Threaded Fasteners
  • What is galling and what types of materials tend to be affected?
  • Examples of fastener threads that have galled, sectioned and x-ray photos.
  • Four ways that galling can be eliminated.

Fatigue failure photo of a bolt Methods of Tightening Threaded Fasteners

Have an understanding of the principles behind each of the following tightening methods:

  • Torque controlled tightening.
  • Torque-angle controlled tightening.
  • Yield controlled tightening.
  • Bolt stretch method.
  • Heat tightening.
  • The use of load indicating methods.
  • The use of ultrasonics to determine bolt loading.
Failure Modes of Threaded Fasteners
  • Learn the differences between a manufacturing and design quality defect.
  • Be able to identify whether a failure is due to a fault in the design specification or is manufacturing related.
  • Learn the 5 main design related failure modes of threaded fasteners and bolted joints.
  • Have knowledge of the critical importance of a fastener's clamp force in ensuring a joint's structural integrity.
  • Why the joint design normally prevents bolt overloading.
  • Learn about fatigue and where failures normally occur on a threaded fastener.
  • Why bearing stress can be crucial in ensuring a reliable joint.
  • Learn about the nature of internal and external thread stripping failures.
Fretting Failure of a bolt Vibration Loosening of Threaded Fasteners
    Have an overview of the research completed over the last 50 years into establishing the cause of self-loosening of threaded fasteners.
    Appreciate the forces that are acting on the threads that tend to self loosen a fastener.

  • Why fine threads can resist loosening better than coarse threads. The inclined plane analogy.
  • Learn about the work completed by Goodier and Sweeney into loosening due to variable axial loading.
  • The work completed by ESNA and the theory of shock induced loosening and resonance within fasteners.
  • The MIL-STD 1312-7 vibration test for fasteners.
  • Junker’s theory on self-loosening of fasteners and why fasteners self-loosen.
  • The Junkers/transverse vibration test for fasteners.
  • The influence that vibration amplitude has on the fastener self-loosening rate.
  • Preload decay curves and the effectiveness of various fastener types in resisting vibrational loosening.
  • The findings of Haviland and Kerley and how fasteners can come loose as a result of bending, shock or impact and differential thermal expansion.
  • Conclusions from the research and how loosening can be prevented.
Fatigue failure photo of a stud Torque Control
  • What is meant by a tightening torque?
  • Units used to measure torque.
  • What are the consequences of not applying sufficient torque to a bolt.
  • How torque is absorbed by a nut/bolt assembly.
  • The torque-tension graph.
  • The relationship between the tightening torque and the resulting bolt preload (tension).
  • The factors which affect the torque-tension relationship.
  • The nut factor method of determining the correct tightening torque.
  • Example calculation of how to determine the correct tightening torque.
  • Scatter in the bolt preload resulting from friction variations.
  • Determining the bolt preload (tension) resulting from a tightening torque.
  • Prevailing torque fasteners (such as those containing a nylon insert) and how they affect the torque distribution and the correct torque to use.

Load Sensing Fasteners

  • The use of strain gauged bolts.
  • The use of load cells.
  • The use of Rotabolts™.
  • The use of Smartbolts™.
  • The use of direct tension indicators (load indicating washers).
  • Squirter™ direct tension indicators.
  • Tension control bolts.
Fatigue failure photo of a stud

Hydraulic Tensioning of Threaded Fasteners

  • The principles behind hydraulic tensioning.
  • The number of tensioners that are used to tighten a joint – 100%, 50%, 33% and 25% tensioning methods.
  • The effect of elastic recovery on the tension induced into a bolt.
  • The use of hydraulic nuts and the sequence used to tighten them.
  • The use of oil filled nuts.
  • The use of rubber filled nuts.
Tightening Procedures

  • The problems of tightening multi-bolt assemblies.
  • Elastic interaction or bolt cross-talk.
  • The use of a tightening sequence.
  • The single pass tightening sequence.
  • Tightening sequences for non-circular bolt patterns.
  • Tests completed to verify tightening sequences.
  • The two pass tightening sequence.
  • The use of multiple tightening tools.
  • Bolt cross talk and hydraulic tensioning.
  • Methods that can be used to check the tightening sequence.
  • The solder plug method.
  • The use of pressure sensitive films.
  • Establishing a tightening procedure.
  • Examples of tightening sequences for circular joints consisting from 4 to 32 bolts are given in the handbook together with an example tightening procedure.

A training course handbook is provided that contains background information to the material presented in the course, together with appendices containing tables of thread size details, fastener material strengths and a glossary detailing the key terms used in bolting technology.

  This training course is also available now, online. Click for details.