6.5 Fasteners Flashcards
How can the thread pitch be determined?
With a screw thread pitch gauge
What does the class of fit indicate?
The tolerance of the thread
What are the classes of fit grades?
Class 1 loose fit through to Class 5 tight fit
What is a class 2 fit?
Free fit
What fit are aircraft bolts manufactured too?
Class 3- Medium fit
What fit are aircraft screws?
Class 2
What is a thread formed on a cylinder called?
Straight or parallel
What is form?
The shape of one complete contour
What is the crest?
The prominent point of the thread
What is the root?
The bottom point of the thread.
What is the flank?
The slope between the crest and root.
What is the thread angle?
The angle between two flanks.
What is the major diameter?
Diameter of the crest
What is the depth?
The radial distance between root and crest.
What is the pitch?
Distance between peaks
What is the lead?
The amount of travel on the thread for one complete turn.
What is run out?
Where the minor diameter merges with the plain shank
What is the helix angle?
Angle of the axis.
Where should single lead threads be used?
When locking power is requireed.
On a single lead thread are the pitch and lead the same?
Yes
What are the three most common threads?
British standard
American National
Unified
What are the four british standard threads?
Whitworth
Fine
Pipe
British Association
What is british standard whitworth?
Standard coarse thread for general purpose
What angle is british whitworth?
55 degrees
What is BSP?
Adaptation of whitworth used for pipe couplings.
What is BA used for?
Fine pitch used for sizes below 6.35mm.
How are BA sizes expressed?
0-10, larger the number the smaller the thread.
What thread angle is BA?
47.5 degrees
What are the two types of american national thread?
Fine and coarse
What is the thread angle of ANC and ANF?
60 degrees
What are the three types of unified thread?
Coarse
Fine
Extra fine
What thread profiles are primarily transmission threads?
Square
Butress
Acme
What increments is the diameter of a bolt given in?
1/16
What increments is the length of a bolt given in?
1/8
What is the grip length?
The part of the bolt that has no thread
What designation does a corrosion resistant bolt have?
C
What designation does an aluminium bolt have?
DD
How is it designated if a bolt is drilled or not for a cotter pin?
The letter A
How is it designated if a bolt is drilled or not for locking wire?
H
Where are clevis bolts used?
Where a shear load is applied.
Where are eye bolts used?
Attachment of turnbuckles or external tension loads.
What are AN73 to AN81 bolts?
Hex-headed nickel-steel bolts for the engine.
What is an internal wrenching bolt?
It has a hex machined into the head so an allen key can be used.
Who developed precision airframe bolts?
NAS
What are all aircraft bolts measured by except AN bolts?
Their grip length
What are the two basic types of nut?
Self locking and non self locking
If more than three threads protrude from a locking nut then what must be done?
A washer under the head
What is the max temp for nyloc nuts?
121 degrees c
As plain nut have no locking ability what is used to lock them?
Spring washerq
What is the purpose of a wing nut?
To allow the nut to be removed frequently without the use of tools
What are tinnerman nuts used for?
Light aircraft to mount instruments
How do you know the correct orientation of a stud?
One end has shorter thread, it is coarser, so when a nut is undone at the other end the coarse thread won’t be loosened.
What types of stud are there?
Standard
Waisted
Stepped
Shouldered
What are the three methods of stud installation?
Stud box
Stud insertion tool
Lock nuts
What can heli coils prevent?
Damage to the threaded hole from consistent insertion and removal
What are the two types of heli coil insert?
Standard type which has a free running insert
Screw lock type
What helps heli coils from not being misaligned?
They are self adjusting
What load carrying does a heli coil have?
across the entire
What are the three classifications of screw?
Machine screws
Structural Screws
Self tapping screws
What are machine screws used for?
Fairings, inspection plates, clamps and other light plates
On a structural screw what are the shank tolerances similar too?
AN hex-head bolts
What heads are structural screws available with?
Fillister
Flat
Washer heads
What four heads are available for self-tapping screws?
Round
Truss
Counter sunk
Counter sunk oval
Where are dowels used?
For precision alignment and correct orientation of two mating surfaces
What types of dowels are used on aircraft?
Smooth solid
Hollow
Threaded
Split hollow
What are some of the methods of locking?
Safety wire
Split pins
Lock washers
Circlips
Quick release fasteners
Keys
How do lock washers work?
The spring action of the washer creates a strong friction force.
What three types of lock washer are used?
Spring
Tab
Shakeproof
How many twists per inch minimum?
6-8
What are pal nuts?
Resilient spring locking action nut made from light-pressed alloy steel which provides a lightweight vibration-proof locking
What three types of quick release fastener?
Dzus, Airloc, Camloc
What two types of Dzus are there?
Light and heavy duty
What are the most common keyway shapes?
Woodruff
Square
Pratt and whitney (sunken)
Gib head (tapered)
How much of a rivet must extend out of the metal?
1.5D
What two systems are in use for rivet codes?
AN system and MS
What increments is the shank diameter in?
1/32
What increments is the length given in?
1/16
Which way round in the code are the diameter and length before and after the dash?
Diameter - Length
What is the most common countersink angle?
100 degrees
What is the recommended head protrusion for a countersink?
0.005 to 0.007 of an inch
What does the rivet marking A denote?
Pure Aluminium
How is the strength of pure aluminium rivet increased?
Cold worked
What does the rivet marking AD denote?
Aluminium Alloy
Why are AD rivets referred to as field rivets?
Because they require no heat treatment.
What does the rivet marking cross denote?
Aluminium alloy with magnesium, they have the letter B in their code
What does the rivet marking dimple denote?
2017 Aluminium Alloy rivet, they are very hard so must be installed frozen.
What does the rivet marking double dash denote?
2024, super hard, have to be stored at -34 degrees to be soft enough for two weeks
What does the rivet marking raised circle denote?
7075 rivet, heat treated zinc ally
What does the rivet marking blank denote?
Corrosion resistant steel, code letter F
What does the rivet marking double dimple denote?
Monel rivet, used as an alternative to cres when high shear strength is not req.
How are titanium rivets denoted and do they require heat treating?
V or T and no
Where is a pop rivet used?
Never on aircraft structure but sometimes used to line a hole up.
Where are cherry friction lock rivets used?
On light aircraft.
How much larger must a cherry friction lock be if it is replacing a solid?
0.8mm
What is the key difference of mechanical lock rivet?
The stem is locked in.
What are some examples of mechanical lock rivets?
Huck
Cherrylock
Olympiclok
Cherrymax
Why are hucklocks generally limited to manufacturers?
Expensive tooling
Can cherry locks replace solids?
Yes
What is the benefit of olympic lok?
They are lightweight, they can be either countersunk or bulbed
What is the advantage of cherrymax that makes them so common?
One tool fits all
What is the ultimate strength of a cherrymax?
50ksi to 70ksi
What is the temp range for cherrymax?
120 to 760 degrees c
How is a mechanical lock rivet removed?
Flat filed onto head and stem punched out. Drill collar. Snap and punch it out.
What three types of lockbolt are in use?
Pull
Blind
Stump
How can you tell a shear lockbolt from a tension lockbolt?
Colour coded collar
What alloys are hi-loks manufactured from?
Titanium
Stainless steel
Steel
Aluminium
What fit should the hole for a hi lok be?
Interference
What is a hi-tigue rivet?
Has a bead at the bottom of the shank that preloads the hole increasing joint strength.
