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Fundamentals of Threaded Fasteners

Fastener experts believe that upwards of 95% of all fastener failures are the result of either the wrong fastener for the job or improper installation. Whether this shocking figure is accurate or not, it is irrefutable that threaded fasteners are poorly misunderstood by many in both the fastener and user communities. In October 1990 the USS Iwo Jima suffered a catastrophic steam valve accident minutes after leaving port following repairs to its steam plant. In one of the single most deadly events of Operation Desert Storm, ten of the eleven crewmen present in the engine compartment would lose their lives. It was later discovered that this accident was the result of improperly chosen fasteners.

Students in this course will explore the basics of threaded fasteners, what purpose specific product design features address, the importance of proper material choices, and the function of platings and coatings. This course will introduce participants to basic fastener engineering principles and explain why tension is all-important in the bolted joint, the relationship between torque and tension, how screws can be used to form their own internal threads, and new technologies and practices being deployed by automotive manufacturers to achieve lighter weight products. This course will include a segment on joining technologies that enable automotive designers and manufacturers to succeed in their light weighting activities. Many of these technologies are relatively new and state-of-the art.

What Will You Learn

By attending this seminar, you will be able to:

Distinguish the different characteristics of threaded fasteners and in what situations/applications those characteristics should be deployed
Explain the relationship between torque and tension in a bolted joint
Differentiate various tightening strategies and assess the most appropriate for specific assembly operations
Distinguish between different material choices and how associated unique material properties lend the designer to use one material over another
Explain how high strength fasteners are achieved
Evaluate the many plating and coating options available for fasteners and make choices that provide the user the greatest amount of value and utility.
Explain the difference between a traditional bolted joint and a joint formed by a thread forming fastener. You will be able to distinguish fundamental differences between the fastener engineering that goes into thread forming in different materials
Evaluate difficult joining scenarios posed by new assembly challenges and assess and apply new joining technologies that will successfully provide a solution

Is This Course For You

This is a basic course and will best be received by those wishing to gain a broad and basic understanding of the topic. It would be very appropriate for both engineers and non-engineers that are in a technical or semi-technical role, who either use, design-in, or provide others with guidance related to fasteners. It would be appropriate for individuals that are new to the industry, have recently moved to a role that requires basic knowledge of fasteners and fastener engineering, or have been in the industry for a while but have never received formal education on fasteners or wish to improve their knowledge of fasteners. This course is NOT for the engineer or designer expecting an in-depth education on designing or understanding the engineering parameters of a bolted joint. While having some limited experience with fasteners and industry terminology will be helpful to the participant, it should not be a prerequisite or deterring factor that would prevent an individual from taking this course. However, if an individual has no knowledge of fasteners or fastener related terminology and struggles understanding basic mechanical concepts, there may be sections of this course that they find difficult to follow or understand.

Materials Provided

This data is not available at this time

Course Requirements

This data is not available at this time

Topics

Day 1

Introductions
- Subject Assessment
- Discussion of specific participant requests/questions
Basics of Fastener Engineering
- Considerations when designing a threaded joint
- Tension versus shear joints
- The Bolted Joint
  - As a spring member
  - Hard versus soft joints
  - Hooke"s Law
  - Pre-tension/Load
- Torque Tension Relationship
  - Is Torque important?
  - Effect of friction (head and thread)
  - T=kDP
  - Effects of lubrication and other surface related conditions
- Tightening Strategies
  - Torque Control
  - Turn of nut
  - Torque/Angle Control
  - Torque/Angle/Yield
  - Ultrasonic Technology
- Loss of tension/Locking Fasteners
  - Prevailing torque
  - Locking versus prevailing torque features
  - On externally threaded fasteners
  - On internally threaded fasteners
- Thread Forming Screws
  - Drive and failure torque behavior
  - Components of driving torque
  - Developing a Tightening Torque
  - Driver repeat accuracy
- Special Considerations in Thread Forming
  - Fastening into Plastics -- Stress sensitivity; Hoop Stress; Relaxation; Boss Design; Driving Speed
  - Fastening into Steel
  - Fastening into Aluminum
  - Fastening into Light Metals
- Joining to Enable Lightweighting
  - Challenges
  - Fastening Thin Sheets
  - Joining Aluminum
  - Joining Dissimilar Materials
  - Carbon Fiber Reinforced Plastics
  - Joining Technologies - Baseline/Traditional Technologies; Flow Drill Screwing; Friction Element Welding; Self-Piercing Rivets; Clinch Technologies

Day 2

Fastener Failure
- Installation
- Corrosion
- Hydrogen Embrittlement
- Torque or Tension Overload
- Fatigue
Manufacturing Flaws -- Surface discontinuities

Threaded Fastener Product Basics
- How Fasteners are made - Video
- Fastener Design Basics -- Design discussion- what are you designing for?
- Screws and Bolts
- Threads
- Nuts
- Washers
- Fastener Materials
- Heat Treating Fasteners
- Plating and Coatings
Wrap-up

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