Fastener Technology

Fasteners in Aviation

• Permanent Fastening
• Discussed previously
• Temporary Fastening
• Threaded
• Non-Threaded 

(Slide 3)
Temporary Fastening

• Threaded and Non-Threaded
• Threaded : Bolts, Studs & Screws

(Slide 4)
Temporary Fastening

• Image of a typical aircraft hardware/fastener cabinet.
• Bins are organized by fastener part number

(Slide 5)
Threaded Fasteners

• Like any other fasteners, threaded fasteners are used to hold parts together. However, unlike any other fasteners, threaded fasteners are able to move part(s) relative to others.

(Slide 6)
Threaded Fasteners

• Image of bolts connecting two sections of a Pratt and Witney PW4098 Turbofan engine.
• The image on the right is a zoom-in of the image on the left
• This engine came from a Boeing 777 airliner, and produces 98,000 lbs. of thrust

(Slide 7)

 Thread Terminology

 

• External (male) thread: Thread cuts outside of the cylindrical body
• Internal (female) thread: Thread cuts inside of the cylindrical body

 

(Slide 8)
Thread Terminology

    

• Crest – Peak edge of thread
• Root – Bottom of thread cut into a cylindrical body
• Thread angle – Angle between threads faces

 

 (Slide 9)
Thread Terminology

  

• Major diameter – Largest diameter on an external or internal thread
• Minor diameter – Smallest diameter on an external or internal thread

(Slide 10)
Thread Terminology

  

• Pitch – Distance between crests of threads

(Slide 11)
Types of Thread Form

• Types of thread form – Profile shape of the thread

(Slide 12)
Thread Standard

• A metric ISO screw thread is designated by the letter M followed by the value of the nominal diameter D and the pitch P, both expressed in millimeters and separated by the multiplication sign “×”. Example: M8×1.25

 

 

(Slide 13)
Thread Drawings

• Detailed Representation

 For detailed representation, crest and roots are drawn using slanting lines or in V shape

 

• Schematic Representation

 For schematic representation, use alternate long and short lines for representing crests and roots respectively

 

• Simplified Representation
• For simplified representation, use thick and thin continuous lines for representing crests and roots respectively

  

(Slide 14)
Bolt Terminology

• Bolt is a threaded cylinder with a head

 

(Slide 15)
Bolt Application

(Slide 16)
Bolt Application - Engine

• Engine case bolt and nut on a Lycoming IO-320 engine
• Nut is on the left hand side, bolt head is on the right

(Slide 17)
Screw Terminology

• Screw Terminology & Application
• Screw is similar to bolt, but has a longer thread than a bolt
• Bolted joint is usually created by turning a nut; screw is installed by turning it.

  

 

(Slide 18)
Screw Application

 

 

(Slide 19)
Screws Application - Fuselage

• Countersunk screws are flush with the skin on this Cessna 310R
• The image on the left is a zoom-in of the image on the right

(Slide 20)
Screws Application - Engine

• Image of exhause shroud screws on a Lycoming IO-320
• Images zoom closer in from right to left
• Exhause shroud is located under the engine, towards the front