1. An AerospaceAn Aerospace
ManufacturingManufacturing
PerspectivePerspective
Introduction to Fastener TechnologyIntroduction to Fastener Technology
Part 3Part 3
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2. Fasteners in AviationFasteners in Aviation
 Permanent Fastening
Discussed previously
 Temporary Fastening
Threaded
Non-Threaded
2

3. Temporary Fastening
 Threaded
– Bolts
– Studs
– Screws
 Non - Threaded
3

4. Temporary Fastening
4
• some common aircraft fasteners
organized by part number

5. Threaded Fasteners
 Use to hold parts together
 Unlike any other fasteners, threaded
fasteners are able to move part(s) relative to
others
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6. Threaded Fasteners
6
• Bolts
connecting two
sections of a
PW4098
Turbofan engine

7. Thread Terminology
 External (male) thread: Thread cuts outside of
the cylindrical body.
 Internal (female) thread: Thread cuts inside of
the cylindrical body.
Internal thread
External thread
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8. Thread Terminology
 Crest – Peak edge of thread
 Root – Bottom of thread cut into a cylindrical
body
 Thread angle – Angle between threads faces
External Thread
CrestCrestRootRoot
Thread angleThread angle
Internal Thread
CrestCrestRootRoot
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9. Thread Terminology
 Major diameter – Largest diameter on an
external or internal thread
 Minor diameter – Smallest diameter on an
external or internal thread
Internal ThreadExternal Thread
Minordia.Minordia.Minordia.
Majordia.Majordia.Majordia.
Minordia.Minordia.
Majordia.Majordia.
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10. Thread Terminology
 Pitch – Distance between crests of
threads
Internal ThreadExternal Thread
PitchPitch
PitchPitch
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11. Types of Thread Form
 Profile shape of the thread
Example :
“knuckle thread form”
Example :
“knuckle thread form”
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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
10.0010.111.7512.00M12
8.508.381.5010.00M10
6.756.651.258.00M8
5.004.921.006.00M6
Tap drill sizeMinor
diameter
PitchMajor
diameter
Nominal
size
10.0010.111.7512.00M12
8.508.381.5010.00M10
6.756.651.258.00M8
5.004.921.006.00M6
Tap drill sizeMinor
diameter
PitchMajor
diameter
Nominal
size
Minor diameter ≈ Tap drill size
Metric thread
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13. Thread Drawings
For simplified representation, use thick and thin
continuous lines for representing crests and
roots respectively:
External thread Internal thread
Pitch/2Pitch/2
RootRoot
CrestCrest
Thread runout
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14. Bolt Terminology
 Bolt is a threaded cylinder with a
head
Hexagonal head
bolt and nut
Head
thickness
Head
thickness
Thread lengthThread length
LengthLength
Width
across flat
Width
across flat
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15. Bolt Application
1. Insert a bolt into
a clearance hole
2. Insert a washer.
3. Screw a nut.
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16. Bolt Application - Engine
16
• Engine case bolt
and nut on a
Lycoming IO-320
engine
• Nut is on the left
hand side, bolt
head is on the right

17. Screw Terminology
 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.
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18. Screws Application
x drill,
CSK to φy
x drill, w deep,
CSK to φy
yy
Draw 90oDraw 90o
1. Drill a hole.
2. Place the screw.
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19. Screws Application - Fuselage
19
• Countersunk screws
are flush with the skin
on this Cessna 310R

20. Screws Application - Engine
20
• Exhaust shroud screws on an IO-320 engine

21. Stud Terminology
Thread length
Length
Thread length
Drawing
representation
21

22. Stud Application
1. Drill a hole.
3. Screw a stud.
4. Place the part to be
fastened.
5. Insert washer and
fastened a nut.
2. Tap a hole.
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