Nuts and bolts
Download
1 / 11

Nuts and Bolts - PowerPoint PPT Presentation


  • 114 Views
  • Uploaded on

Nuts and Bolts . Threaded Fastener Issues: Types Materials/Grades Tightening Torque. Threaded Fasteners. Did you know that? the Boeing 747 uses about 2.5 million fasteners 70,000 titanium costing $150,000 400,000 other fasteners costing about $250,000

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Nuts and Bolts' - lucretia


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Nuts and bolts
Nuts and Bolts

Threaded Fastener Issues:

  • Types

  • Materials/Grades

  • Tightening Torque


Threaded fasteners
Threaded Fasteners

Did you know that?

  • the Boeing 747 uses about 2.5 million fasteners

    • 70,000 titanium costing $150,000

    • 400,000 other fasteners costing about $250,000

    • 30,000 squeeze rivets, 50cents each installed

  • In certain applications (such as an engine head), you should tighten the bolt as much as possible, if it does not fail by twisting during tightening, there is a very good possibility that the bolt will never fail


Why are fasteners used
Why are fasteners used?

Advantages

  • Removable

  • Easy to install

  • Wide variety of standard parts

    Disadvantages

  • loosening

  • failure

  • cost


Types
Types

  • Machine screws

  • Wood screws

  • Tapping screws


Standard thread systems
Standard Thread Systems

Unified or American ACME

SI (ISO)

Pipe Whitworth (UK)


Typical designation
Typical Designation

1/2” - 13 UNC - 2A

Terminology of screw threads

Sharp vee threads shown for

clarity; the crests and roots are

actually flattened or rounded

during the forming operation.

external thread

(B means internal)

Class of fit

(1 is loosest tolerance, 3 is tightest)

Thread Series

UNC (Unified Coarse)

UNF (Unified Fine)

Pitch (threads/inch)

Nominal Diameter

(also shown as decimal or screw #)


Bolt grades
Bolt Grades

  • Grade indicates the tensile strength of the bolt

  • Determined by bolt material and heat treating


Tightening torque
Tightening Torque

It is typical on engines for bolts to have a specified tightening torque. Why?

  • It results in a quantified preload on the bolts

  • Insures that parts never separate

  • Maintains friction (no sliding to shear forces)

  • Insures even distribution of loading

    • prevent warpage of mating parts

    • uniform pressure distribution over seal or gasket

  • Prevents bolt from loosening

  • Reduces fatique effects


Bolt manufacturing processes
Bolt Manufacturing Processes

  • Forging (upsetting)

  • Rolling

a)

b)

Thread-rolling processes: a) reciprocating flat dies; and b) two-roller dies.

Threaded fasteners, such as bolts, are made economically by these

processes at high rates of production


Manufacturing processes continued
Manufacturing Processes - continued

  • Turning on screw machines

(a) Differences in the diameters of machined and rolled threads. (b) Grain flow in machined and rolled threads. Unlike machining, which cuts through the grains of the metal, rolled threads have improved strength because of cold working and favorable grain flow.


References
References

  • Kalpakjian, S. Manufacturing Engineering and Technology, 2nd Edition, Addison Wesley, 1992.

  • Spotts, M.F., Design of Machine Elements. Prentice-Hall, Inc., 1985.

  • Shigley, Joseph and Mitchell, Larry, Mechanical Engineering Design. McGraw-HillBook Company, 1983.


ad