Fasteners in the Aerospace Industry:
Introduction to Fastener Technology,
Part 3
Lecture Notes
(Slide 2)
Fasteners in Aviation

Permanent Fastening
o Discussed previously

Temporary Fastening
o Threaded
o Non-Threaded
(Slide 3)
Temporary Fastening

Threaded and Non-Threaded
o 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
1
(Slide 7)
Thread Terminology
External thread
Internal thread

External (male) thread: Thread cuts outside of the cylindrical body

Internal (female) thread: Thread cuts inside of the cylindrical body
(Slide 8)
Thread Terminology
External Thread
Internal Thread
Thread angle
Crest
Root
Root
Crest

Crest – Peak edge of thread

Root – Bottom of thread cut into a cylindrical body

Thread angle – Angle between threads faces
(Slide 9)
Thread Terminology
Minor dia.
Major dia.
Internal Thread
Major dia.
Minor dia.
External Thread

Major diameter – Largest diameter on an external or internal thread

Minor diameter – Smallest diameter on an external or internal thread
2
(Slide 10)
Thread Terminology
External Thread
Internal Thread
Pitch
Pitch

Pitch – Distance between crests of threads
(Slide 11)
Types of Thread Form
Example :
“knuckle 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
Nominal
size
M6
M8
M10
M12
Major
diameter
Pitch
Minor
diameter
Tap drill size
6.00
8.00
10.00
12.00
1.00
1.25
1.50
1.75
4.92
6.65
8.38
10.11
5.00
6.75
8.50
10.00
Metric thread
Minor diameter ≈ Tap drill size
3
(Slide 13)
Thread Drawings

Detailed Representation
o For detailed representation, crest and roots are drawn using slanting lines or in
V shape
External thread
Internal thread
Thread runout
Pitch

60o
Schematic Representation
o For schematic representation, use alternate long and short lines for
representing crests and roots respectively
Internal thread
External thread
Thread runout
Pitch

60o
Simplified Representation
o For simplified representation, use thick and thin continuous lines for
representing crests and roots respectively
External thread
Internal thread
Thread runout
Pitch/2
Root
Crest
4
(Slide 14)
Bolt Terminology

Bolt is a threaded cylinder with a head
Thread length
Length
Hexagonal head
bolt and nut
Width
across flat
Head
thickness
(Slide 15)
Bolt Application
2. Insert a washer.
3. Screw a nut.
1. Insert a bolt into
a clearance hole
(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
o Screw is similar to bolt, but has a longer thread than a bolt
o Bolted joint is usually created by turning a nut; screw is installed by turning it.
5
(Slide 18)
Screw Application
1. Drill a hole.
x drill,
CSK to y
x drill, w deep,
CSK to y
Draw 90o
y
2. Place the screw.
(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
(Slide 21)
Stud Terminology

Studs
Thread length
Thread length
Drawing
representation
Length
6
(Slide 22)
Stud Application
1. Drill a hole.
2. Tap a hole.
3. Screw a stud.
4. Place the part to be
fastened.
5. Insert washer and
fastened a nut.
Review of
Fasteners in the Aerospace Industry:
Introduction to Fastener Technology
At the conclusion students should be able to:
 Demonstrate an understanding of the different types of fastening: permanent and
temporary
 Demonstrate an understanding of thread terminology such as external and external thread,
and pitch
 Demonstrate an understanding of thread drawings terminology such as detailed,
schematic, and simplified representations
 Demonstrate an understanding of bolt terminology and application.
 Demonstrate an understanding of stud terminology and application.
 Demonstrate an understanding of screw terminology and application.
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