Threaded Fastening Systems per NASA-STD-5020


Just about everyone involved in developing hardware for space missions (or any other purpose, for that matter) has been affected by problems with mechanical joints. Common problems include structural failure, fatigue, unwanted and unpredicted loss of stiffness, joint slipping or loss of alignment, fastener loosening, material mismatch, incompatibility with the space environment, mis-drilled holes, time-consuming and costly assembly, and inability to disassemble when needed. The objectives of this course are to

  • Build an understanding of how bolted joints behave and how they fail
  • Impart effective processes, methods, and standards for design and analysis, drawing on a mix of theory, empirical data, and practical experience
  • Share guidelines, rules of thumb, and valuable references
  • Help you understand the new NASA-STD-5020

Includes a close look at NASA-STD-5020, Requirements for Threaded Fastening Systems in Spaceflight Hardware, which was approved in March 2012 for use throughout NASA.

Also, the course includes many examples and class problems. Participants should bring calculators.

Who should attend:

Mechanical design engineers, structural analysts, and others interested in or involved with bolted joints.

Course Outline:

  1. Overview of Designing Fastened Joints
    • Common problems with structural joints
    • A process for designing a structural joint
    • Identifying functional requirements
    • Selecting the method of attachment
    • General design guidelines
    • Introduction to NASA-STD-5020
    • Key definitions per NASA-STD-5020
    • Top-level requirements
    • Factors of safety, fitting factors, and margin of safety
    • Establishing design standards and criteria
    • The importance of preload
  2. Introduction to Threaded Fasteners
    • Brief history of screw threads
    • Terminology and specification
    • Tensile-stress area
    • Are fine threads better than coarse threads?
  3. Developing a Concept for the Joint
    • General types of joints and fasteners
    • Configuring the joint
    • Designing a stiff joint
    • Shear clips and tension clips
    • Avoiding problems with fixed fasteners
  4. Calculating Fastener Loads
    • How a preloaded joint carries load
    • Temporarily ignoring preload
    • Other common assumptions and their limitations
    • An effective process for calculating bolt loads in a compact joint
    • Examples
    • Estimating fastener loads for skins and panels
  5. Failure Modes, Assessment Methods, and Design Guidelines
    • An effective process for strength analysis
    • Bolt tension, shear, and interaction
    • Tension joints
    • Shear joints
    • Identifying potential failure modes
    • Fastening composite materials
  6. Thread Shear and Pull-out Strength
    • How threads fail
    • Computing theoretical shear engagement areas
    • Including a knock-down factor
    • Test results
  7. Selecting Hardware and Detailing the Design
    • Selecting compatible materials
    • Selecting the nut: ensuring strength compatibility
    • Common types of threaded inserts
    • Use of washers
    • Selecting fastener length and grip
    • Recommended fastener hole sizes
    • Guidelines for simplifying assembly
    • Establishing bolt preload
    • Torque-preload relationships
    • Locking features and NASA-STD-5020
    • Recommendations for establishing and maintaining preload
  8. Mechanics of a Preloaded Joint
    • Mechanics of a preloaded joint under applied tension
    • Estimating bolt stiffness and clamp stiffness
    • Understanding the loading-plane factor
    • Worst case for steel-aluminum combination
    • Key conclusions regarding load sharing
    • Effects of bolt ductility
    • How temperature change affects preload
  9. Analysis Criteria in NASA-STD-5020
    • Objectives and summary
    • Calculating maximum and minimum preloads
    • Tensile loading: ultimate-strength analysis
    • Separation analysis
    • Tensile loading: yield-strength analysis
    • Shear loading: ultimate-strength analysis
    • Shear loading: ultimate-strength analysis
    • Shear loading: joint-slip analysis
    • Revisiting the bolt fatigue and fracture requirement
  10. Summary


  • It was a fantastic course—one of the most useful short courses I have ever taken.

  • Interaction between instructor and experienced designers (in the class) was priceless.

  • (The) examples (and) stories from industry were invaluable.” Everyone at NASA should take this course!

  • Your presentation skills are excellent, with patient attention paid to class questions.

  • Great course! Lots of lessons learned. The examples made it that much better.


This course is not on the current schedule of open enrollment courses. If you are interested in attending this or another course as open enrollment, please contact us at (410)956-8805 or at and indicate the course name and number of students who wish to participate. ATI typically schedules open enrollment courses with a lead time of 3-5 months. Group courses can be presented at your facility at any time. For on-site pricing, request an on-site quote. You may also call us at (410)956-8805 or email us at


  • Tom Sarafin has worked full time in the space industry since 1979. He worked over 13 years at Martin Marietta Astronautics, where he contributed to and led activities in structural analysis, design, and test, mostly for large spacecraft. Since founding Instar Engineering in 1993, he’s consulted for NASA, DigitalGlobe, Lockheed Martin, AeroAstro, and other organizations. He’s helped the U. S. Air Force Academy design, develop, and verify a series of small satellites and has been an advisor to DARPA. He was a member of the core team that developed NASA-STD-5020 and continues to serve on that team to help address issues with threaded fasteners at NASA. He is the editor and principal author of Spacecraft Structures and Mechanisms: From Concept to Launch and is a contributing author to Space Mission Analysis and Design. Since 1995, he has taught over 200 courses to more than 4000 engineers and managers in the space industry.

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