6.5- Fasteners Flashcards
A thread formed on a cylinder is a straight or parallel thread, what is called on a conical part?
Tapered thread.
What is the definition of screw form?
Shape of the thread from crest to crest.
What is the crest of a thread?
The most prominent part.
What is the root of a thread?
The bottom point of the thread groove.
What is the flank of a thread?
The slope of the thread between root and crest.
What is the thread angle?
The angle between two adjacent flanks.
What is the major diameter of a thread.
Male- diameter of crest
Female- diameter of roots
On a male thread what is the major diameter also referred to as?
Crest or normal diameter.
What is the depth of a thread?
The radial distance between root and crest.
What is the pitch of a thread?
The distance between adjacent crests.
What is the lead of a thread?
The distance a crest travels in one complete revolution.
What is thread run out?
The part of the thread which starts at the minor diameter until it equals the major and meets the plain shank of the fastener. (Basically the last bit of the thread).
When you increase amount of starts in a fastener (threads) what happens to how far it travels in one revolution?
It travels further, for example a 2 start will travel twice as far as a single start.
What did British and Americans use as their screw standards.
British- BS and BA
America- AN
What have the the UK and US thread systems been replaced by for one system?
Unified thread.
What do the three British standard thread forms BSW, BSF and BSP stand for?
British standard Whitworth
British standard fine
British standard pipe.
What is the thread of BSW.
Coarse with a thread angle of 55 degrees.
What is the thread of BSF.
Finer version of the coarse BSW.
What is the thread of BSP.
Even finer version of BSW and BSF.
What size is BA threads used for?
Anything below 1/4, its thread angle is 47.5 degrees.
What are BA sizes expressed in?
0-10, the larger the number the smaller the thread.
What is the major diameter of a BA 0 thread?
0.236 inches.
What are the two types of American national thread (AN).
ANC- coarse
ANF- fine
What are the three versions of unified threads?
UNC- Coarse
UNF- Fine
UNEF- Extra fine
What’s different about an ANC thread?
Has flat crests and roots.
What is the main difference between a coarse and fine pitch?
Coarse pitch will travel further in one revolution although a fine pitch will have stronger grip and better adjustment.
What is the most common thread profile?
Symmetrical vee thread.
What are the other three common thread profiles and what are they commonly used for?
Square, buttress and Acme.
Transmission threads.
On a bolt head what does a a x top left denote?
Steel
On a bolt head what does a a x in a triangle denote?
Steel close tolerance
On a bolt head what does a a - denote?
Corrosion resistant steel (CRS)
On a bolt head what does a a - and triangle denote?
Corrosion resistant steel close tolerance.
On a bolt head what does a a - - denote?
Aluminium.
On a bolt head what does a a - triangle - denote?
Aluminium alloy, close tolerance.
How is the NAS6405 U 6 (X) broken down?
NAS6405- basic part no.
U- unplated
6- grip length
X- 1/64 oversized
In a bolt identification where X is 1/64 oversize what is a Y?
1/32 oversized
What is the grip length measured in and what would a 6 represent?
16ths
6/16 = 3/8
In bolt identification if U denotes unplated what does -, D, and H denote?
- -Plated
D- Drilled shank
H- Drilled head
How is the bolt identification BACB30NE 5 D H 8 X broken down?
BACB30- Basic Part no. NE- Long thread 5- Nominal diameter 5/16 D- Drilled shank H- Drilled head 8- Grip length 8/16
In general what should the grip length equal?
Material thickness
If a material thickness is less than 2.4mm then how many threads can be within the hole?
None
How can a grip length be adjusted?
The use of washers, a maximum of three can be used.
What is a stud?
A piece of rod with a thread at each end, its installation and removal requires special tools.
What are the 4 different types of stud?
Standard
Waisted
Stepped
Shouldered.
Where are waisted studs used?
Where the strength has to be retained but weight saving is required.
Where are stepped studs used?
To provide a stronger anchorage than plain studs.
When are shouldered studs used?
When maximum rigidity is required against lateral stress.
What methods are there of stud installation?
Stud box
Stud insertion tool
Lock nuts
If a stud is damaged how should it be removed?
Filed flats or Ezi-out
What are the most commonly used machine screws?
Flush head, round head, fillister head, socket head, pan head and truss head.
What head angles do flush head come in?
They are countersunk so 82 and 100 degrees.
Where are pan and truss head screws used?
Where head height is unimportant.
What are the 4 different classes of nut?
Non self locking
Locking
High temp self locking
Low temp self locking.
What are non self locking nuts used with?
Drilled shank, hex head, clevis, eye and strut bolts designed to accommodate a cotter pin or locking wire.
Where are shear castle nuts used?
Only on shear load clevis bolts.
Where are castle nuts used?
To fit onto standard airframe bolts and may be used where subject to shear or tensile loads.
Where would you find a wing nut?
On hose clamps and battery connections, where the desired tightness is finger tight.
What is a lock nut?
A thin plain nut tightened down onto the main nut. The friction wedges the threads preventing them from slackening.
What is a nyloc stiffnut?
Has an unthreaded nylon insert, when it is engaged it cuts the nylon and the friction prevents it coming undone, they must be replaced when removed.
What is a oddie stiffnut?
It has 6 tongues bent to slightly less than the root diameter, they provide a locking load.
What are aerotight and philidas stiffnuts?
They have slotted locking extensions these align with the thread and produce a friction lock.
How far should a low temp self locking nut threads extend through a nut?
1/32 inch.
Bolts over 5/16 inch diameter with cotter pin holes may be used with self locking nuts, on what condition?
The hole is free of burrs.
What is the tolerance of a heli coil flats?
0.0005mm
What are the two types of heli coil available?
Standard type with free running thread
Screw lock type with resilient internal locking thread.
Heli coil allow full load distribution, compared to what percentage on the first thread in an ordinary thread?
45-50%
What are the 6 common methods of locking device?
Wire locking Cotter pins Lock washers Locking plates Snap rings Self locking nuts
What two methods of lock wiring are there?
Single or double twist.
How is a spring washer used?
Fitted beneath the nut so that when the nut is tightened the spring is compressed and sets up a locking friction.
How is a tab washer used?
Has two or more tabs, one is bent up against the flat of a nut.
What is a shakeproof washer?
It has serrations that allow it to be tightened but they are resistant to be undone.
What are the 4 principle parts of a camloc?
Receptacle
Grommet
Retaining Ring
Stud assembly
In a camloc what does the stud assembly consist of?
Stud
Cross pin
Spring
Spring cup
What two types of Dzus fasteners are there?
Light duty- box covers and access holes
Heavy duty- cowlings and heavy fairings
What material is an A rivet? And how are they identified?
1100 Aluminium
No identifying mark
What material is an AD rivet? And how are they identified?
2117 Aluminium
Small dimple
What material is an D rivet? And how are they identified?
2017 Aluminium
Raised dot
What material is an DD rivet? And how are they identified?
2024 Aluminium
Two dashes
What material is an B rivet? And how are they identified?
5056 Aluminium
Raised cross
What material is an F rivet? And how are they identified?
CRES
No marking
What material is an M rivet? And how are they identified?
Monel
Two dimples or raised R
What material is an T rivet? And how are they identified?
Titanium
Raised V or T
How is the rivet designation MS20470 AD5-12 broken down?
MS20470- MS part number
AD- material
5- diameter
12- length.
What are the two parts of hi-lok and hi-lite fasteners?
Threaded pin with a head
Collar with internal thread.
What must you ensure before the Hi lok or hi lite is installed?
Correct type
Correct material
Correct surface protection or lubrication
Correct grip length
Where are taper locks used?
Areas of structure where a high fatigue performance is required.
Who can install taper locks?
Approved operators.
When working with lockbolts what are they supplied with and what most you do?
They are supplied lubricated and it must not be removed.
What must you do when a lockbolt can’t be used because of a limited space hi-lok?
Refer to SRM chapter 51 for an acceptable alternative.
What are the three types of blind rivet used?
Standard cherrylock
Bulbed cherrylock
Oversize cherrylock.
What two types of head are available with blind rivets?
100 degree countersink and protruding head.
Which chapter can you use in the SRM for reference on blind rivets?
51
What fastening system is a bulbed cherrylock?
Complete shear.
Where would you use a oversized cherrylock?
Where the rivet holes have become enlarged. They come in 1/64 oversize for each diameter.
What are pop rivets classed into?
BH (Break head)
BS (Break Stem)
Why are pop rivets less suitable on aircraft?
Because they loosen under vibration.
In the part number for pop rivets e.g. AGS2051/537/BS, what does the 537 represent?
Rivet diameter 5/32 and rivet length 0.37”
What are Avdel heads available in?
Snap head and 100/120 degree countersunk.
How are avdels installed?
Avdel pliers or Avdel Riveter.
What are Avdel rivets manufactured in?
L86 Aluminium Alloy either natural colour or dyed violet.
What is used as an alternative to Avdel’s.
Cherry MBC
What does a cherry mbc assembly consist of?
MBC rivet sleeve and stem.
What is the definition of grip length?
Combined thickness of the material to be joined.
What is an olympic-lok rivet?
Light three piece mechanically locked spindle type blind fastener.
What should you never do to olympic-lok rivet?
File the stem as it will weaken the mechanical lock
What is a rivnut an combination of?
Rivet and nut.
