Fasteners Flashcards
What is a screw thread?
Ridge cut into screw
What is the thread in clockwise?
Right hand thread
What is the thread in anti-clockwise?
Left hand thread
What is the form of a screw thread?
Shape of one complete contour of thread between corresponding points in the crest
What is the crest?
Prominent point of thread whether male or female
What is male?
External thread
What is female?
Internal thread
What is the root?
Bottom point of thread groove
What is the flank?
Slope of thread between root and crest
What is the thread angle?
Angle between two adjacent flanks
What is the major diameter in…
Male?
Female?
Male - the diameter of the crest
Female - the diameter of the root
What is the minor diameter in…
Male?
Female?
Male - the diameter of the root
Female - the diameter of the crest
What is the depth?
Radial distance between root and crest
What is the pitch?
Crest to crest
What is the lead?
Distance moved in one turn
Single start thread - lead is same as pitch
What is the runout?
Part of thread where minor diameter increases until it equals the major diameter (the plain part)
What are thread forms?
Formed by one continuous groove (in a single start thread)
Double start thread - double distance covered
Triple start thread - triple distance covered
What does BS stand for?
British Standards
What does BA stand for?
Angle?
British Association
47.5 degrees
What does BSW stand for?
What is it for?
British Standard Whitworth
General purpose
What does BSF stand for?
Used for?
British Standard Fine (fine threads)
High vibration
What does BSP stand for?
Used for?
British Standard Pipe
Pipeline couplings
What is the smallest screw?
Used for?
Anything under 1/4” diameter
Used for small electrical parts
What does ANC stand for?
American National Coarse
What does ANF stand for?
Angle?
American National Fine
60 degrees
What does UNC stand for?
Unified National Coarse
What does UNF stand for?
Unified National Fine
What does UNEF stand for?
Unified National Extra Fine
What is the Unified angle?
Identification?
60 degrees
Rings like olympics
Which thread will have a stronger lead than fine pitch?
Coarsed pitch
Three types of thread pitch?
Square thread
Butteress thread
Acme thread
What is the most common thread used?
Symmetrical V thread
How is a bolt tightened?
With a nut
How is a screw tightened?
Into a threaded hole
How do you install a bolt or screw?
Install so if they are loose, they remain head upwards/in direction of rotation
How much thread should be showing?
0.8mm
Typical fasteners?
Hexagon drilled (1 hole) Internal wrenching Internal wrenching drilled Hexagon slotted 100 degrees countersunk (cross recess) Cylindrical hexagon wrenching Pan (cross recess) Hexagon drilled (6 holes) 12 point extended washer
Most part numbers will break down into what?
Grip Length Diameter Drillings Finish
What does X stand for?
Steel
What does X in a triangle stand for?
Steel, close tolerance
What does a - stand for?
Corrosion resistant steel (CRS)
What does - and a triangle stand for?
CRS, close tolerance
What does - - stand for?
Aluminium
What does -triangle- stand for?
Aluminium alloy, close tolerance
What does U stand for in a code?
Unplated
What does - stand for in a code?
Plated
What does D stand for in a code?
Drilled shank
What does H stand for in a code?
Drilled head
What does the number after the letter mean in a code?
Grip length
Grip length of a bolt should equal what?
Thickness of material
Materials of more than 2.4mm have what?
Two threads inside hole
Materials less than 2.4mm have what?
No threads inside hole
What is the maximum number of washers used to overcome grip strength?
3
What is a standard stud?
Threaded all the way
What is a waisted stud?
Threaded on each end
What is a shouldered stud?
Threaded on each end and a ring in the middle
What is a stepped stud?
Threaded on each end, thicker at one end
What are studs classified by?
Diameter
Length
Thread type
Three types of stud fittings?
Stud box
Stud insertion/removal tool
Lock nuts
Methods of stud removal
Lock nuts
Filed flats
Ezi-outs
Properties of self-tapping screws
Thin gauge sheet metal parts
Drilled holes
Generates own thread
Slotted and cruciform head types
What is a Shear Castle Nut?
Used same as castle but, but in areas that have lower tensile loads
What is a Castle Nut?
Used with drilled shanks and locked with a split pin
What is a slotted engine nut?
Designed to be put in high temperature areas
What is a wing nut?
Internal, finger tightened nut. Used for frequently opened areas
What is a plain nut?
Takes high tensile loads. Requires locking device
What is a check nut?
Used as a locking device for plain nuts
What is a lock nut?
Thin, plain nut. Tightened firmly onto main nut, wedges both onto threads. Friction lock
What is a Nyloc Stiffnut?
Unthreaded Nylon insert. Friction prevents loosening. Low temperature only
What is an Oddie stiffnut?
Six springey tongues, bent inwards, forms a circle less than diameter of root of bolt thread, grips bolt thread
What are Aerotight and Philidas?
Slotted locking extensions, misaligned threads, realigned by bolt thread, grips thread
What type of slit does Aerotight have?
Vertical slit
What type of slit does Philidas have?
Horizontal slit
What are Anchor nuts?
Types?
Fixed nuts, riveted
Two-leg anchor nut One-leg anchor nut Corner anchor nut Right-angle anchor nut High-temp two-leg anchor nut Two-leg floating anchor nut Ganged or strip anchor nut
What are High-temp self-locking nuts?
Used in 120C+ areas CRES, Steel alloy, silver plated CRES Friction locking Threads out of phase Pinched thread end section
What are Low-temp self-locking nuts?
Used in 121C Max areas Smaller diameter Fibre/nylon insert Bolt thread cuts own thread tapping into insert, at least one thread showing through the nut Do not use if finger tightened
Two types of Heli-Coil Inserts?
Standard free running Screw lock (internal locking)
What are Heli-Coils manufactured from?
Round wire into diamond profile
How to install Heli-Coils?
Drill hole
Special thread tapping
Thread gauge (go/no-go)
Fit Heli-coil - insert key, engage tang in driving slot, no downward pressure, at least 1/2 pitch below surface, snap off tang
How to remove Heli-coils?
Bend top coil inwards, creating a tang, unscrew, use an insertion tool/pliers, may use tapered left hand tap of correct size which grips internal threads, post removal examine hole threads prior to filling new insert
Safetying methods
Wire locking Split pins Lock-washers Locking plates Snap-rings (circlips) Self-locking nuts
Two wire-locking methods?
Single - small screws, closed geometric pattern, electrical systems, hard to access areas
Double - preferred, twist/inch 8-10 twists
Three types of washers?
Spring Washer - single/double coil spring, friction set up
Tab Washer - anchors on component, tab bends over a flat. Do not reuse
Shakesproof Washer - spring Steel, slanting serrations, sharp edges prevent unscrewing, reusable
Types of locking devices?
Pip-pin Camloc Dzus Airloc Split pin
What is a pit-pin?
Non threaded
Quick
What is Camloc?
Four principle parts: Receptacle Grommet Retaining ring Stud assembly
What is Dzus?
Two types: Light duty (access covers, etc) Heavy duty (cowlings, etc)
Spring
Stud
Grommet (heavy only)
What is Airloc?
Receptacle riveted to access panel frame
Stud
Cross pin
Fixed and floating types
What is Split pin?
Materials:
Low Carbon
Stainless steel (CRES)
Measured to shortest prong
CRES non-magnetic areas (compasses)
Good fit - not loose
What do keys do?
Agreed standard taper?
Transmit drive from lock shaft to hub when mating surfaces are smooth. Used in parts that don’t require frequent separation
1:100
Four types of keys?
Hollow or flat saddle
Gib-headed
Feather
Woodruff
What is a hollow/flat saddle?
Not suitable for heavy loads
What is a Gib-headed?
Sits on the end, locks everything in place
What is Feather?
When axial movement is required between hub and shaft
What is Woodruff?
Fits in like the letter D
Which rivets are used “as fabricated”?
What are they used for?
1100 Aluminium
Attach aluminium components where low strength is needed
Which three rivets are heat treated and used when medium strength is needed?
2017, 2117, 7050
Which rivets are supplied in -T4 condition, need heat treated, and are used when high strength is needed?
2024
What are Monel Rivets?
Without heat treatment before use, are used in steel, titanium, or aluminium alloy riveted assemblies
What are Titanium Rivets?
Rivets with a cylindrical or a partially tapered shank. No heat treatment
What must rivet shear strength match?
The bearing strength
Usually the rivet diameter is at least…
3x sheet thickness
Four types of rivets?
Snap head
Universal
Mushroom
Countersunk (100 degrees is used)
What is 1100?
Letter?
Head marking?
Aluminium
A
No marking
What is 2017?
Letter?
Head marking?
Aluminium alloy
D
Raised dot
What is 2117?
Letter?
Head marking?
Aluminium alloy
AD
Small dimple
What is 2024?
Letter?
Head marking?
Aluminium alloy
DD
Two raised dashes
What is 5056?
Letter?
Head marking?
Aluminium alloy
B
Raised cross
Which aluminium alloys need heat treated?
2024 DD 2017 D (?)
What letter is used for CRES?
Head marking?
F
No markings
What is sometimes used instead of CRES?
Letter?
Head marking?
Monel
M
Two dimples
Raised “R”
What is the letter for Titanium?
Head marking?
T
Raised “V”
Or raised “T”
What does M52040 AD - 5 - 12 mean?
20 - universal head
AD - Material designation 2117 T4
5 - diameter in 32nds
12 - length in 16ths
What are Hi-lok fasteners?
Tools?
Two parts:
Threaded pin with a lead universal or CSK
Collar with internal thread and shear groove
Tools: Allen key (holds pin) Hex drive (turns collar)
The axis of the fastener hole must be perpendicular to the surface on which the fastener lead will sit
On a Hi-lok, what do aluminium collars max at?
CRES collars?
3 degrees
0.5 degrees
How to install Hi-loks?
Check grip length
Pins and collars match
Lubricate if required
Install by hand or power
What are the collar colours?
Oversizes?
Red - 1/64
Black - 3/64
Blue - 1/32
Chromium plate - varies
What are Hi-lites?
Very similar to hi-loks
Less material
15% lighter than hi-lok
Weight saving
What are Taper-loks?
Tapered bolt and self locking nut
Used in high fatigue areas
Good sealing effect
Do not remove lubricant
What are Lockbolts?
Strong and light Two piece assembly - pin and collar Ensure collar face is correct way Wet-installed with sealant Do not remove lubricant
What are Cherrylock Blind rivets?
Three types:
Standard
Bulbed
Oversize
Body, pin, locking collar
Do not remove lubricant
What are Cherrymax rivets?
Two types:
Cherrymax
Oversize cherrymax
One piece
Body, pin, collar
Driving anvil detaches - protects tooling
How to measure grip length?
Put scale in hole
Hook onto rear face of material
Read thickness
What are Olympic-lok rivets?
Light
Three piece mechanically locked
Never file stem - weakens lock
Only use Olympic tools
What are Rivnuts?
Rivet and nut combination
Creates a threaded location allowing screw fit in thin sheet metal
