6.5 Fasteners✅(12) Flashcards
The screw thread pitch on a screw, bolt or tapped hole can be determined and measured with what
- a screw thread pitch gauge
Why is it important to periodically check all thread gauges?
to ensure they are not worn beyond allowable limits or damaged
Class 1 fit is a
loose fit
Class 2 fit is a
free fit
Class 3 fit is a
medium fit
Class 4 fit is a
close fit
Class 5 fit is a
tight fit
Generally, aircraft screws are manufactured with what class fit?
Class 2 (free fit)
Generally, aircraft bolts are almost always manufactured with what class
Class 3 fit (medium)
What class fit requires a wrench to turn a nut on to a bolt
Class 4 (close fit)
What class can be turned with fingers?
Class 1
When cut in clockwise, the thread is said to be?
right hand
When cut is is anti-clockwise, the thread is said to be?
left hand
Most screws and bolts have single lead threads (T or F)?
T
What are double, triple and quadruple threads also known as ?
multiple lead threads
What thread screw should be used when locking power is required
single lead thread
What is the lead
- distance that a nut travels in 1 revolution
What is pitch?
distance from a point on 1 thread to the corresponding point on the next thread
What are the 3 most common thread standards
- British standard thread forms
- American National (AN) thread forms
- Unified thread forms
What are the 4 British standard thread forms?
- British standard whitworth (BSW)
- British standard fine (BSF)
- British standard pipe (BSP)
- British Association (BA)
What are the 2 American National (AN) thread forms
- ANC (American national coarse)
- ANF (American national coarse fine)
What are the 3 unified thread forms?
UNC - Unified National Coarse
UNF - Unified National Fine
UNEF - Unified National Extra Fine
What is the thread angle for American national thread forms
- 60*c
Coarse pitch screws would have less threads (T or F)
T
Fine pitch screws would have more threads (T or F)
T
What is a bolt designed to do
hold 2 or more items together
What shape bolts are typically used for airframe structural applications?
Hex heads
What is the bolts grip length?
length of unthreaded portion
What are aircraft bolts available in
-cadmium plated nickel steel
- corrosion-resistant steel
- 2024 aluminium alloy
Unless specified, what is the bolt made of
cadmium plated nickel steel
Generally, what does the marking on the head of a bolt identify?
identifies what the bolt is made out of
British standard whiteworth is coarse, general purpose and rapid dismantling (T or F)
T
British standard fine is finer than BSW, resists vibration (T or F)
T
What is the thread angle of British standard whitworth?
55*
What British thread form is used to resist vibration
British standard fine
What is the thread angle of British association (BA)
47.5*
What does BSP stand for
British standard pipe
Acme threads is made up at an angle of?
29*
What are square thread profiles used for
Power transmission
ACME thread is stronger than the square thread (T or F)
T
What are buttress thread profiles designed to handle?
heavy forces in one direction
When are clevis bolts used
when load applied is in shear
The diameter of a clevis bolt is given in?
1/16 inch (1.6mm) increments
Where are eyebolts used
where external tension loads are to be applied
The head of a eyebolt is specifically designed for the attachment of a turnbuckle which connects 2 wires together (T or F)?
T
What are close tolerance bolts
grounded to a tolerance of +0.000 - 0.0005 inch
Where must close tolerance bolts be used?
-areas that are subject to pounding loads
What mark is indicated on top of a close tolerance bolt
- triangle mark
Where would you use internal wrenching bolts?
-areas subjected to high tensile loads
What wrench does a internal wrenching bolt accept
Allen wrench
Internal wrenching bolts have greater strength than a standard steel AN bolt (T or F)
T
The precision airframe bolts were developed and updated by whom
- NAS (National aerospace standards)
All aircraft bolts except for AN bolts are measured by their grip length and not by their overall length (T or F)
T
What are the 2 basic type of nuts
- self locking
- Non self locking
Self locking nuts have a locking device to keep them from coming loose (T or F)
T
What does non-self locking nuts rely on?
relies on cotter pin, check nut or lock washer to hold it in place
If more than 3 threads are exposed when using a self locking nut, what should you do
- replace bolt with correct length
- install a washer
What are the 2 general self locking nuts used in aviation?
- fibre
- nylon type (low temp)
Nylon self locking nuts must not be used in any location where temperature could exceed what temperature
121c (250F)
Nylon self locking nuts must not be used in any location where temperature could exceed 121c (250F). However they can be used on engines, in locations specified by the manufacturer (T or F)
T
What is used when temperature exceeds 121c (250F)?
- metal lock nuts are used
How is a corrosion resistant nut identified?
- by the letter C
How is a aluminium alloy nut identified?
- by the letter D
When is a castle nut used
when bolt is subjected to either shear or tensile loads
The castle nut is designed to fit on a standard airframe bolt with a class 3 fit (T or F)
T
What is shear castle nuts used for
-Shear loads on clevis bolts
What does a plain nut require to prevent the nut from shaking loose?
spring-type lock washer
What is a check nut
- a second nut that is tightened against a primary nut
What are check nuts made out of
cadmium plated steel
What is a engine nut not approved for?
- airframe use
Engine nuts are made out of heat treated steel and has national fine threads that produce a class 3 fit (T or F)?
T
When is a wing nut used
when parts require frequent removal without the use of tools
What class fit does wing nuts provide
class 2
What are aircraft wing nuts made of?
-cadmium plated steel
-brass
A stud is a shaft that is threaded at both ends (T or F)
T
What does Heli-coil insert prevent
-Prevents thread from wear due to continual insertion and removal of both bolts and screws
Heli-coil inserts are available for all thread standards (T or F)
T
What is the Heli-coil tolerance?
- 0.0005mm (0.0002in)
Heli-coil inserts allow each thread to adjust to the screw (T or F)
T
The first threads of a Heli-coil insert, carries how much load in percentage?
45%-50%
What are the 3 basic classification of screws?
- Machine screws
- structural screws
- Self-tapping screws
Machine screws are extensively for attaching fairings, inspection plates, fluid line clamps, and other light structural parts (T or F)
T
What is the main difference between aircraft bolts and machine screws?
- Threads on machine screws usually run the full length of the shank
How are structural screws made
- made of alloy steel and are heat treated
What type of thread does a self tapping screw have
- coarse
What is the self tapping screws used for?
- to hold thin sheets of metal, plastic, or plywood together
What is a type A screw (self tapping screws)?
- Sharp point
What is a type B screw (self tapping screws)?
- Blunt point
What are the 4 types of heads available on self tapping screws
- Round head
- Truss head
- Counter sunk
- Counter sunk oval screw
What can dowels be made out of
- wood, plastic, or metal
What is a dowel used for?
- Precision alignment of 2 mating surfaces
What are the 3 commonly used lock washers in the aviation industry?
- spring
- tab
-shakeproof
Lock washers are made of steel and are twisted so that when a nut is tightened against it, the spring action of washer creates a strong friction force (T or F)
T
What is a spring washer
- when tightened, spring is compressed and creates friction which prevents nut from vibrating loose
How many tabs does a tab washer have
-Has 2 or more tabs
How does a tab washer work
- one tab is bent against one flat nut
- other tab is bent over an edge/slot or hole
Can you re-use a tab washer
No
How is the shakeproof washer preventing the tendency to unscrew?
- By the sharp edges of the serrations
Can a shakeproof washer be re-used
yes providing they retain their springiness
What is lock wire commonly made out of
- Stainless steel
Lock wiring is critical and used where inspection intervals may be infrequent (T or F)
T
Lock wiring must have 6-8 twists per inch (T or F)
T
What are the 3 common quick release fasteners
- Dzus
- Camlock
- Airloc
What are the 2 types of Dzus fasteners
- light duty
- heavy duty
What is the main difference between the 2 types of Dzus fasteners
- Heavy duty fasteners have a grommet
What are the 2 types of Airloc receptacles available?
- fixed type
- floating type
The floating type (airloc) enables easier alignment (T or F)
T
What can Camloc fasteners be referred as
quarter turn fasteners
What does a quick turn fastener usually consist of
- Stud (male)
- Washer
- Receptacle (female)
What are circlips used for
retaining shafts, seals and bearings
Special pliers are used to install or remove a circlip (T or F)
T
A key is a specially shaped piece of metal, which is a hardened piece of metal that fits into cut outs (keyways) in wheels, discs, sprockets or gears (T or F)
T
What is the most used technique to join aluminium?
riveting
Before a rivet is driven, it must extend beyond the base material at least x1.5 rivet diameter (T or F)
T
What is the common countersink angle?
100*
What is the rivet code for universal head?
AN470
What is the rivet code for round head?
AN430
What is the rivet code for countersunk rivets
AN426
What is dimpling
- Process that mechanically ‘dents’ the sheet to accommodate for rivet head
What are the majority of aircraft rivets made of
aluminium alloy
What are the 4 lock rivets
- Huck Loks
- Cherrylock
- Olympic loks
- Cherry max
What were Huck Lok used for
- structural replacements for solid shank rivets
Olympic Lok blind fasteners are light weight, mechanically locking spindle type blind rivets (T or F)
T
Why would you use a CherryMAX rivte
- economical
- strong enough to replace solid shank rivets
What are lockbolts used for
- To assemble 2 materials permanently
What are the 3 lockbolts used in aviation
- Pull-type
- Blind-type
- Stump-type
Lockbolts are available for both shear and tension lockbolts (T or F)
T
Taper-Lok are the strongest special fasteners used in aircraft construction (T or F)
T
what is run out?
Part of the thread where the thread transitions to the shank
A bolt drilled for wire locking would be identified by
Letter H following part number
A self locking nut must be screwed onto a bolt until all the chamfer on the bolts end protrudes through the insert or:
at least one, but not more than 3 threads, protrude through the nut
What are ganged anchor nuts
Floating type anchor nuts installed in channel riveted to the structure
Maximum number of bolts secured together by locking wire is
3
What are the 2 common head shapes for solid shank rivets
Universal and countersunk
What are the 4 types of studs
- Standard
- waisted
- stepped
- shouldered
