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An Aerospace An Aerospace Manufacturing Manufacturing
PerspectivePerspective
Introduction to Fastener TechnologyIntroduction to Fastener Technology
Part 3Part 3
1
Fasteners in AviationFasteners in Aviation
Permanent FasteningDiscussed previously
Temporary FasteningThreadedNon-Threaded
2
Temporary Fastening
Threaded– Bolts– Studs– Screws
Non - Threaded
3
Temporary Fastening
4
• some common aircraft fasteners organized by part number
Threaded Fasteners
Use to hold parts together Unlike any other fasteners, threaded
fasteners are able to move part(s) relative to others
5
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.
Internal thread
External thread
7
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
8
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
Min
or d
ia.
Min
or d
ia.
Min
or d
ia.
Maj
or d
ia.
Maj
or d
ia.
Maj
or d
ia.
Min
or d
ia.
Min
or d
ia.
Maj
or d
ia.
Maj
or d
ia.
9
Thread Terminology
Pitch – Distance between crests of threads
Internal ThreadExternal Thread
PitchPitchPitchPitch10
Types of Thread Form
Profile shape of the thread
Example :
“knuckle thread form”
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
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 sizeMetric thread12
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
13
Bolt Terminology
Bolt is a threaded cylinder with a head
Hexagonal head
bolt and nutHead
thicknessHead
thickness
Thread lengthThread length
LengthLength
Width across flat
Width across flat
14
Bolt Application
1. Insert a bolt intoa clearance hole
2. Insert a washer.
3. Screw a nut.
15
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
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.
17
Screws Application
x drill,CSK to y
x drill, w deep,CSK to y
yyDraw 90oDraw 90o
1. Drill a hole.
2. Place the screw.
18
Screws Application - Fuselage
19
• Countersunk screws are flush with the skin on this Cessna 310R
Screws Application - Engine
20
• Exhaust shroud screws on an IO-320 engine
Stud Terminology
Thread length
Length
Thread length
Drawing
representation
21
Stud Application
1. Drill a hole.
3. Screw a stud.
4. Place the part to befastened.
5. Insert washer andfastened a nut.
2. Tap a hole.
22