An Aerospace An Aerospace Manufacturing Manufacturing

PerspectivePerspective

Introduction to Fastener TechnologyIntroduction to Fastener Technology

Part 3Part 3

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Fasteners in AviationFasteners in Aviation

Permanent FasteningDiscussed previously

Temporary FasteningThreadedNon-Threaded

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Temporary Fastening

Threaded– Bolts– Studs– Screws

Non - Threaded

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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

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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

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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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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.

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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”

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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

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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

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Bolt Application

1. Insert a bolt intoa clearance hole

2. Insert a washer.

3. Screw a nut.

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Bolt Application - Engine

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• 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.

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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.

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Screws Application - Fuselage

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• Countersunk screws are flush with the skin on this Cessna 310R

Screws Application - Engine

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• Exhaust shroud screws on an IO-320 engine

Stud Terminology

Thread length

Length

Thread length

Drawing

representation

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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.

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