Introduction to Fastener Technology
Part 3
An Aerospace
Manufacturing
Perspective
1
Fasteners in Aviation

Permanent Fastening
 Discussed

Temporary Fastening


2
previously
Threaded
Non-Threaded
Temporary Fastening

Threaded
–
–
–

3
Bolts
Studs
Screws
Non - Threaded
Temporary Fastening
4
• some common aircraft fasteners
organized by part number
Threaded Fasteners


5
Use to hold parts together
Unlike any other fasteners, threaded
fasteners are able to move part(s) relative to
others
Threaded Fasteners
6
• Bolts
connecting two
sections of a
PW4098
Turbofan engine
Thread Terminology


External (male) thread: Thread cuts outside of
the cylindrical body.
Internal (female) thread: Thread cuts inside of
the cylindrical body.
External thread
Internal thread
7
Thread Terminology
External Thread
Internal Thread
Thread angle
Root
Root
Crest

Crest – Peak edge of thread
Root – Bottom of thread cut into a cylindrical
body

Thread angle – Angle between threads faces

8
Crest
Thread Terminology
9
Internal Thread
Major dia.
Minor dia.
External Thread
Major dia.

Major diameter – Largest diameter on an
external or internal thread
Minor diameter – Smallest diameter on an
external or internal thread
Minor dia.

Thread Terminology

Pitch – Distance between crests of
threads
External Thread
Internal Thread
Pitch
10
Pitch
Types of Thread Form

Profile shape of the thread
Example :
“knuckle thread form”
11
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
12
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
Thread Drawings
For simplified representation, use thick and thin
continuous lines for representing crests and
roots respectively:
External thread
Internal thread
Thread runout
Pitch/2
Root
13
Crest
Bolt Terminology

Bolt is a threaded cylinder with a
head
Thread length
Length
Hexagonal head
bolt and nut
14
Width
across flat
Head
thickness
Bolt Application
2. Insert a washer.
1. Insert a bolt into
a clearance hole
15
3. Screw a nut.
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
16
Screw Terminology


17
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.
Screws Application
1. Drill a hole.
2. Place the screw.
x drill,
CSK to y
18
Draw 90o
y
x drill, w deep,
CSK to y
Screws Application - Fuselage
• Countersunk screws
are flush with the skin
on this Cessna 310R
19
Screws Application - Engine
• Exhaust shroud screws on an IO-320 engine
20
Stud Terminology
Thread length
Thread length
Drawing
representation
Length
21
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.
22