6.5 fasteners Flashcards
What can be used to measure the screw thread pitch?
A screw thread pitch gauge
How do you know if the thread pitch has been identified?
If the gauge matches up with the thread
What are screw thread pitch gauges used for?
To identify external or internal screw threads
What does the class of fit indicate?
The tolerance
What does Class 1-5 mean?
Class 1 loose fit
Class 2 free fit
Class 3 medium
Class 4 close
Class 5 tight
What class are aircraft bolts normally?
Class 3
What does a class 4 fit require that a class 1 fit doesn’t?
A wrench, whereas a class 1 can turned with fingers
What class are aircraft screws manufactured in?
Class 2 thread fit
What is BSW summed up?
British standard course thread which is recommended for general purpose works in metal and plastic
What about the BSW thread makes it suitable for quick assembling and disassembling of components?
The Whitworth thread
What are the features of a BSW?
It has a symmetrical vee shape and an angle of 55 degrees and is roused weekly at the root and the crest
What is BSF summed up?
It is a finer version of the Whiteworth thread form
What two important features related to a finger thread do BSF have?
It increases the resistance against vibration and creates a finer form of adjustment
A BSF screw will always have more screws per what?
2.5cm
What is BSP summed up?
Another finer thread adaptation of the Whitworth thread form
Where are a BSP used?
In pipe couplings
What can ensure a BSP has a pressure tight joint?
What can ensure a BSP has a pressure tight joint?
What does the fine pitch ensure on BSP?
Uncut metals remain on the wall of a pipe
What is BA summed up?
A fine pitch thread used for 6.35 (1/4) in diameter only
What is BA used for?
Smaller mechanical and electrical parts
What is different about expressions in BA?
They’re expressed numerically
in BA threads, what is the popular size range?
0-10
In BA threads, the larger the number….
and the smaller the number….
The smaller the thread
The larger the thread
Why does the BA differ in terms of degrees?
What is retained?
47.5 degrees
The feature of equal rounding for root and crest
What are the American standard threads?
ANF
ANC
What are the features of AN thread forms?
The flattening of the crest and root in the AN is not equal and the thread angle sits at 60 degrees.
What are unified thread forms?
Incorporates features from British and American national threads
Are the differences in the American and British interchangeable?
Yes
What are the three versions of UN?
UNC
UNF
UNEF
What does the shape or profile of the screw thread depend upon?
Its job
What is the symmetrical vee thread designed to combine?
Strength with ease of engagement
What do square roots have powerful of?
Roots
What are square threads used for?
Carrying heavy loads, transfer of power and exerting, screw jack and vice spindle
The specific measurement or number per inch of threads are not what in square roots?
Particular
What are buttress threads?
They have a triangular section, one face at the right angle and the other is sloped
What power do buttress threads have?
Pulling
What are ACME threads summed up?
Similar to square threads but are tapered
What are ACME threads summed up?
Similar to square threads but are tapered
Because of ACME’s slanted ends, what is made easier?
easier to fix or unscrew the split nut but do not have backlash in it
What is ACME’s degrees?
29 degrees
What are squares ideal for?
Ideal thread for power transmissions
Is acme stronger than square threads?
Yes
What are the buttress threads designed for?
Designed to handle forces in one direction
(eg true jack)
What does a nut act as?
Secure it in place
What is a boot used for?
To hold two or more items together
What is a bolts diameter increments in?
What is a bolts length increments in?
1/16
1/8
What type of heads do bolts have?
Hex
What does the diameter of a bolt equalate to?
The Diameter of the shank
What is a bolts grip length?
The length of the unthreaded portion
When must washers be added to a bolt and why?
If the grip length is slightly longer than the total thickness of the material
What can result in a weaker joint?
When the thread goes into the material because the grip length is less than the thickness of the material (thread goes in)
What does ‘A’ mean in a bolt?
It is not drilled for a split pin
What is the diameter in, AN3-6A
What is the length?
What does ‘A’ mean
3 diameter in 1/16
6 length in 1/8
It does not have a hole for a split pin
How do you know if it is drilled for a split pin?
There is no letter
How is a corrosion resistant bolt identified?
With the letter C (in between length and diameter)
How are aluminium alloys identified?
DD
How does a cadmium plated nickel steel look?
A star
How does corrosion resistant bolt look?
A single dash
How does 2024 aluminium bolt look?
Two dashes
What do bolts have marked on their heads?
Material identification NDT manufacturer’s data
What size does the FAA forbid?
AN3
What are not allowed to be used in sea planes?
Aluminium alloy nuts used with cadmium plated steel bolts in shear
What AN bolts must be wire locked?
Fastening propellers
A wire locking bolt has what letter?
H
When are clevis bolts used?
in shear
What AN is clevis bolts?
AN21 AN36
What does a clevis bolt look like?
It has a domed head that is slotted
what is a unique feature of a clevis bolt?
Only a small portion of the shank is threaded
What does the small notch between the threads and shank do?
Long grip length which increases the bolts shears strength and allows the bolt to move more freely
What is the length and diameter of a clevis pin?
1/16
What AN are eye bolts?
AN42 AN49
AN42 AN49
Where external tension loads are to applied
What is the head of an eyebolt specifically designed for?
Attachment of turnbuckle which connects two cables
What is the threaded shank drilled for?
Safe tying
What AN are drilled head engine bolts?
AN73 AN81
What is different about drilled engine heads?
They are thicker and have drilled heads in the centre of the head and around the flats
What is the diameter of a drilled engine head?
What is the length?
1/16 increments
1/8 increments
What AN are close tolerance bolts?
AN 173 AN186
What is the close tolerance bolts tolerance?
+0.000 -0.0005 inch
Where are close tolerance bolts used?
In areas prone to pounding or in a structure that is about to be rivited or bolted
How can you recognise a close tolerance bolt?
It has a triangle on its head
When are internal wrenching bolts used?
When are internal wrenching bolts used?
What sided hole is drilled into internal wrenching bolts?
6 sides to accept an Allen wrench
What must occur to the hole when installed in steel parts to accommodate the radius?
Counterbore
When an internal wrenching bolt is installed in aluminium structure, why must a washer be used?
To pre de needed bearing area.
What must an AN bolt never be substituted for?
An internal wrenching bolt
What are the NAS length increments?
1/8
Where is the grip length measured on a NAS bolt?
Beneath the head end of the thread
What are odd dash numbers?
Special application bolts
What are odd dash number’s grip length longer than?
1/16
When are odd dash numbers used?
Where a standard MS bolt is either too long or too short
What does the basic NAS number identify?
The part
What are most aircraft’s bolts measured by?
Their grip length
How do AN bolts bolts differ in terms of measuring?
They’re measured by their overall length
What are MS bolts’ dash numbers like?
Even
Where are odd dash numbers available in MS bolts?
When the grip length is critical and a standard grip is either too long or too short
Where must the load be on an MS bolt?
On the shank not on the thread
What must you refer to when purchasing fasteners?
Aircraft illustrated parts
how many numbers are NSA specification?
Is a four digit number
What is the first dash in the four digit specification in NSA?
What is the second dash number?
The diameter in 1/16 increments
1/16 in grip length
Where are studs installed?
In internal threads in a casting or built up assembly
If internal threads are damaged, what are the two alternatives?
To repair the part or repair and replace the threads
What does Heli Coil protect against?
Wearing because of continuous insertion
Heli coils are available for what type of thread standards?
All
What sort of cross section does helicoils have?
Diamond cross section
When will the tang break off?
When it reaches a certain tension
What are the two types of Heli coil?
The standard types
The screw lock type
What is a standard type of Heli coil?
Provides a free running thread
How do Heli coil inserts compensate for their lead and angle errors?
They self adjust
What is a screw lock type Heli coil?
Provides a resilient internal lock thread
How do screw’s differ from bolts?
They are made from a lower strength materials
What threads are screws fitted with?
A loose fitting thread
What are the head shapes of screws made for?
To engage a screwdriver or wrench
What are the three basic classifications of screws?
Machine screws
Structural screws
Self tapping screws
What do structural screws have the same strength as?
Bolts
What are self tapping screws used for?
To join lightweight materials
What are machiene screws used for?
Attaching light structural parts such as fairings or fluid lines
What is the main difference between aircraft’s screws and bolts?
Threads of machine screws run the full length of the shank
Bolts have a unthreaded grip length
What class fit do machine screws have?
Class 2 (loose fit)
What are the most common machiene screws used in aviation?
Fillister screws, the round head screws, the flat head screw the truss head screw
What are structural screws made out of?
Alloy steel that are heat treated
What else can stuctural screws be used for?
Structural bolts
What are structural screws available with?
Fillister flat or washer heads
What are the threads used in structural screws?
National fine, hex head bolts
What must you never use on a torque set screw?
A Philips screwdriver
What must you never use on a Hi torque screw?
A slotted screwdriver
What threads do self tapping screws have?
Course threads
What are self tapping screws used for?
To hold thin sheets of metal plastic or plywood
What does type A self tapping screws have?
A gimlet (sharp point)
What does type B self tapping screws have?
A blunt point with thinner threads
What are the four types of heads available on self tapping screws?
Round head
Truss head
Countersunk
Countersunk oval
What is different between the round head screw and the truss head screw?
The truss head screw is thinner
What is a dowel?
A solid cylindrical rod
What is a dowel called in its original manufactured form?
A dowel rod
When are dowels used?
Where precision alignment and correct orientation of two mating surfaces is required.
Smooth solid dowel pins are made with high quality steel metallic to ensure what?
Smooth solid dowel pins are made with high quality steel metallic to ensure what?
What are split hollow dowels used for?
To maintain alignment and act as bushing for rotating
What do structural screws have the same grip strength as?
Bolts of the same size
When is a lock washer used?
If the joint is not structurally critical
What is a lock washer?
The spring action of the washer creates friction
What is a spring washer?
A double coil spring or single coil with sharp edges. it is compressed and creates friction
What is a tab washer?
Two or more tabs that are suitable for a plain nut
Can you re use a tab washer?
No
What is a shakeproof washer?
a spring steel washer with slanted serrations on its internal or external surface
Why is there an angle of serrations in a shakeproof washer?
For the nut to ride them and cut into them
Can you reuse shakeproof washers?
Yes if they retain its springiness
Where are drilled head bolts often used?
In vibration prone areas
What is the wire diameter measured in?
1/1000
What is a minimum of twists per inch?
6-8 twists per inch
In critical areas where a number of bolts must be secured by wire what is the maximum number of bolts?
3
How are locking plates secured to the structure?
They’re secured to an adjacent sort
What are lock plates held in place by?
Shakeproof washers and tab washers
Can lock plates be reused?
yes if they remain good fit
What are pal nuts?
They’re a spring locking action nut which provides lightweight vibration proof in low profile
Are pal nuts designed to be with or without a standard nut?
Both`
Where are pal nuts idea in use?
Where frequent load changes tend to loosen conventional nuts
What are quick release fasteners?
They provide vibration resistance for quick and repetitive attatchment and removal of panels with minimal effort
What does locking and unlocking a quick release faster require?
A quarter turn or push
What are the two types of Dzus fasteners?
Light duty type
Heavy duty types
What are light duty type fasteners?
Used on box covers, access hole covers and lightweight fairings
What are heavy duty fastners?
Used in cowlings and heavy fairings
What is the main difference between the two Dzus fastners?
A grommet is used with heavy duty fastners
What does the airloc consist of?
A receptacle, a stud and a cross pin
What are the two types of airloc?
The fixed type
The floating type
What does the floating type consist of?
Easier alignment of the stud into the receptacle
What can Camloc fastners be referred to?
Quarter turn fastners
What are camloc designed to do?
They’re designed to connect quick and easy in confined spaces
What helps to save time in Camloc?
Turn latches
What are Camlocs resistant to?
Vibration
The quick turn fastners usually consist of what?
A stud a washer and receptacle
What is a pip pin?
They’re non threaded fastners allowing the rapid installation and removal of parts without tooling
What are the two versions of pip pins?
Locating and locking version
What are rung pull detect pins?
A single ball locates the pin, no positive pin. For locating purposes
What is a double acting steel pin?
To release the ball lock mechanism. The ring handle can be pushed in or pulled out
What are circlips?
A spring clip used for internal and external washing
What are cir clips used for?
Retaining shafts seams and bearings
What are used to open or compress the circlips?
Special pliers
What are taper pins?
Is a joint that is created for shear loads that does not allow any loose motion or play
What are roll pins?
They are used to provide propping for a joint where the pin is not likely to be removed
What is a roll pin made up of?
It is cylindrical but the ends or not joint which helps it to compress in the joint
What are clevis pins used for?
Hinge Pins
How do you remove a roll pin?
With a pin punch
What are clevis pins increments?
What are clevis pins increments?
What pins are inserted into clevis pins?
Split pins
What must never happen with split pins?
They must never be over torqued to make the holes align
What must happen if the nut fails to align with the drilled bolt hole?
Add washers until a split pin can be inserted
What is a key?
Formed metal that fits into cut outs
What is the advantage of Woodruff key?
Once it is placed in the part, it is unable to move
What is a square key?
They tend to move out of their slots unless placed by a locking fastner
What is a Pratt and Whitney key?
Once it is placed in the part it is unable to move. Also known as the Sunken key
What is the gib head key?
It’s tapered and driven in place
What governs insertion depth and allows removal?
The tang
What does the gib head key require?
Retention in critical applications
What are the two self locking nuts used in aviation?
The fibre or the nylon type
What can happen if three threads are exposed in self locking nuts?
It can bottom out and create a stress point
What corrective action must you take if it bottoms out?
You must replace the bolt or add washers
What are low temperature self locking nuts not meant to be used in?
Temperature must not excited 122
What are self locking nuts held in place by?
A nylon insert
What are low temperature self locking nuts class in terms of fit?
Class 3
Self locking nuts must not be used where?
In tension only shear
What must be used when temperature exceeds 121?
Metal lock nuts must be used
What do metal lock nuts look like?
The nut has a smaller diameter compared to the boys to grip the bolt
When are castellated nuts used?
Class 3 shear or tensile loads
What does a shear castle nut have the same type thread as?
AN310
What are different about shear castle nuts?
They’re only used for shear so are much thinner
What do plain nuts not have?
Castellations so can’t have a split pin so must use a spring type washer instead
What loads do plain nuts require?
Shear and tensile
What is a plain nut locked in place with?
A check nut
What is a check nut?
A second nut that tightens it
What is a check nut?
A second nut that tightens it
Where are light hex nuts used?
In non structural appliances requiring light tension and they need a locking device to secure them
What class fit are engine nuts?
class 3
What does a plain engine nut not have?
Holes for split pins
What size does a plain engine nut fit?
11.1
When is the use if a wing nut necessary?
To remove a part frequently without the use of tools
What is a lock nut?
Two nuts are screwed onto the outer thread if the stud
What do anchor nuts do?
They’re permenantly mounted nuts that enable inspection plates and access doors to be completely removed
What is a stud?
A shaft that is threaded at both ends but one is a long thread the other is shirt thread
What is the short thread?
A coarse thread and a much tighter fit than the long thread
When are studs used?
Where joints have to be broken frequently
What does a stud not have?
A head
What is a standard stud?
Most commonly used. They have the same diameter for the threaded major diameter and the unthreaded portion
When is a waisted stud used?
Where strength has to be retained but weight saving is required
Where is a stepped stud used?
Provide stronger anchorage and used as replacements for plain studs
What are shouldered studs?
Maximum rigidity is required against lateral stresses
What is a stud box?
A hexagonal metal bar
What is a stud insertion or removal tool?
The stud is started into the thread, the stud and tool turn together
What are tinnerman nuts?
Theyre stamped out of sheet metals
What are tinnerman nuts used for?
Riveted to a structure to hold screws and used to secure inspection plates
What is a rivet?
A type of fastener that obtains its clamping actions by having one if it’s sides mechanically upset
What happens when a rivet is driven?
The cross sectional area increases along with its bearing and shear strength
How much must a rivet extend out of the material before driven?
1.5cm
How much does the bucktail surface?
1.5cm
After riveted, how much must the rivet extend?
One half the original diameter
What does the first part of the code denote?
The rivets organisation
What the second part represent?
Rivet alloying material
What is the third digit?
The diameter indicated in 1/32
What is the fourth digit called?
The length indicated in 1/16
How is the length of a universal head rivet measured?
The bottom of the head to the end of the shank
How is the head of a countersunk rivet measured?
From the top of the head to the end of the shank
What is the countersink angle?
100 degrees
What is dimpling?
Mechanically denting the sheets that are joined to accommodate the rivet head
When installing a countersunk head rivet, how much is the head meant to protude?
0.005 to 0.007 of an inch
If the head provides after firming, what can happen?
A rotary micro shaver can be used to flush the rivet head
What is a left hand image?
If the rivet head is allowed to protude above the metal. The rivet guns energy hits the head resulting in a stronger joint
What is a right hand image?
If a countersunk rivet is set with the rivet head flush with the surface, some of the rivet guns driving energy is lost
What Is aluminium represented as?
A
What is 2117 aluminium alloy known as?
AD with a dimple in his head.
Theyre always known as field rivets and have a dimple in the head
What is 5056 Aluminium Alloy known as?
B. They have a raised cross on their head
What is 2017 Aluminium alloy known as?
D. Extremely hard and have a raised dot in the centre of their head
What is the new version of 2017 aluminium called?
The crack free rivet alloy
Why must 2017 alloy be reheat treated?
They’re too hard to be driven one hour after heat treated
How is intergranular oxidisation of 2017 Ally oxide prevented?
Its anodised before the first reheat treatment
How can 2017 be soft enough to be used for several days?
By putting it in the freezer below 0 degrees
What temp are 2017 Ally alloys subjected to when heat treated?
499 to 510 for 30 minutes and immediately quench in water
2024 Aluminium Alloys are identified how?
DD and two raised dashes
How is 7050 designated?
With an E and raised circle
How is Corrosion resistant steel designated?
No markings on the head and with the letter F
When are Monel rivets used?
Instead of CRES When their lower shear strength is not a cause of damage
What are Monel rivets identified with?
Two recessed dimples in their head, M
What are titanium rivets?
Cylindrical or partially tapered shank
Is heat treatment titanium rivets heat treated?
No
How are titanium rivets identified?
Raised T or V
What requires access to both ends?
Conventional solid shank rivets
What requires access to one side?
Special or blind rivets
What are pop rivets?
They’re never used for structural repairs
What are pop rivets known for?
They’re useful for lining up holes
What were cherry friction locks’ styles?
Hollow and self plug in
What are cherry friction lock rivets two head styles?
Universal and 100 degree
When a friction lock is used to replace a solid rivet how much larger must it be in diameter?
1/32
What are mechanical lock rivets designed to do?
To prevent the centre stem of the rivet from falling out
What is the difference between friction lock and mechanical lock rivets?
Mechanical lock rivets permanently locks the stem into place
What are Huck loks used for?
Structural replacement for solid shank rivets
What are Cherry lock rivets?
Their centre stem is locked into place with a lock ring
What does installation of a cherry lock require?
A special pulling tool
What’s a disadvantage of cherry lock rivets?
If a rivet is too short for application the lock ring sets prematurely resulting in a malformed shank header
What do removal of special fasteners involve?
Removal of the washer nut or locking collar
What do you remove special fastners with?
Proper sized box end wrench or vice grips
What is a Hi Tigue fasteners?
They have a bead that encircles the bottom of the shank
What does the bead do in Hi Tigue?
It preloads the hole it fills resulting in stronger joints
What are taper locks?
Strongest. Exerts a force on the conical walls of a hole
What are Hi Lites?
Same as Hi locks but made from a lighter material and has a shorter transition from the thread to the shank
What are the benefits of Hi lite?
Good strength to weight ratio, weight saving with no loss of strength
What do lockbolts conform to?
Military standards
What are lockbolts used for?What are lockbolts used for?
To bond two materials permanently
Are lockbolts heavy or leightweight?
Leightweight
What are three types of lockbolts used in aviation?
Pull type
Blind type
Stump type
How do you fit a Hi lok bolt?
The hole is first drilled with an interference fit, the Hi Lok is then tapped into the hole and a shear collar is installed
What do Hi lok bolts withstand?
Bearing and shearing loads
