6.5 Flashcards
what are the 5 different classes of fit
class 1- loose fit
class 2- free fit
class 3- medium fit
class 4- close fit
class 5- tight fit
what class of fit are most aircraft screws
class 2
what class of fit are most aircraft bolts
class 3
what is the definition of a bolt
tightened with a nut
what can be used to tell how many threads per inch
a thread pitch gauge
what is the difference between right and left hand threads
right hand threads are cut clockwise and left hand are cut counter clockwise
what is the crest of a thread
the prominent point of the thread
what is the root of a thread
the lowest point of the thread
what is the flank of a thread
the angle from root to crest
what is the major diameter of a thread
on male thread its crest to crest and on female thread its root to root
what is the minor diameter of a thread
on a male thread its root to root and on female thread its crest to crest
what is the pitch of a thread
the distance between 2 of the same point eg crest to crest
what is the lead of a thread
the distance a screw moves for one complete rotation
what are the negatives of using multiple threads
less holding power and less force produced when tightened
what are the characteristics of British standard whitworth thread forms
55° thread angle, coarse thread used for general purposes
what are the characteristics of British standard fine thread forms
55° thread angle, fine threads mainly used in high vibration areas
what are the characteristics of british association
47.5° thread angle used on very small electrical parts under 1/4 inch diameter
what are the characteristics of american national thread forms
60° thread angle with flat crests and roots
what are the characteristics of unified thread forms
incorporates both american and British features 60° thread angle
what is the difference between coarse and fine threads
coarse threads have a lot more distance between each thread whereas fine has a lot less
what are the 3 other types of thread profiles
square, ACME, buttress
what is the definition of a screw
tightened into a threaded hole
what is the diameter and length measured in for Airforce Navy
length in 1/8 inch and diameter in 1/16 inch
what does the letter A signify in Airforce Navy
the absence of a split pin hole
what does the letter H signify in Airforce Navy
there is holes for wirelocking
what are the 3 main materials aircraft bolts are available in
cadmium plated nickel steel
corrosion resistant steel
2024 aluminium alloy
Unless specified what material is a bolt made from
cadmium plated nickel steel
What does the letter C signify in a bolt
its made from corrosion resistant steel
what does DD signify in a bolt
its made from 2024 aluminium alloy
what is a clevis bolt used for
shear loads
what is the diameter and length of a clevis bolt measured in
both in 1/16 inch
what is an eye bolt used for
tensile loads
what are the characteristics of a close tolerance bolt
ground to a much tighter tolerance and used in areas subject to pounding loads
what are the characteristics of internal wrenching bolts
high strength steel bolts used primarily in areas with high tensile loads
what must be installed with an internal wrenching bolt when its installed in aluminium structures and why
a washer to spread the load so its not concentrated on a small point
what is the length measured in for NAS precision airframe bolts
even numbers are 1/8 inch and odd numbers are 1/16 longer than the even before it
how is the length of an AN bolt different to the same length of another bolt
AN measure overall length and other bolts measure grip length
what is the length of an MS bolt measured in
1/8 inch is even numbers and odd numbers between can be available when the length is critical
what are the measurements for NSA
1/16 inch for both length and diameter
what are the 2 basic types of nuts
self locking and non self locking
how does a self locking nut work
increases friction within the thread by changing the metallic structure or having nylon at the end
when is a low temperature nut used and how does it increase thread friction
below 121°C and have nylon to increase friction
when is a high temperature nut used and how does it increase thread friction
above 121°C and have a change in metallic structure
what class of fit is a castle nut and what does the number indicate
class 3 fit and number denotes size of bolt that fits
what is the main characteristic of a shear castle nut
much thinner than a castle nut used for shear loads usually put on clevis bolts
what type of bolt is a plain nut used for
a bolt that doesn’t have a hole for split pins so has an A
what is a check nut used for and what are its characteristics
making sure the primary nut cannot turn off and is about half the thickness of the plain nut and rotates in the opposite direction
what makes an engine nut unique
rounding of the castles
when is a wing nut used
to remove something without tools
what are anchor nuts and when are they used
permanently mounted nut plates for areas that cannot be accessed from the back
what are tinnerman nuts used for
instrument mounts on light aircraft
what are rivnuts
a rivet that becomes an anchor nut when it is formed
what are the 4 types of stud
standard, waisted, stepped and shouldered
what are the 2 uses for a helicoil insert
reinforce thread in soft material to stop stripping and spread the load more, to repair stripped thread
what are the 3 basic classifications of screws
machine, structual and self tapping
when are machine used
light structural parts and they are the most widely used
what type of screw can be directly substituted with a bolt
structural screw
what are self tapping screws used for
holding thin sheets together
what are the 2 types of self tapping screws
type A which has a sharp point
type B which has a blunt point and fine threads
what is a dowel and when is it used
a cylindrical rod used for precision alignment and orientation
what are the 3 types of lock washsers
spring, tab and shakeproof
what does a spring washer do
the spring compresses when the nut is tightened increasing friction
how does a tab washer work
it works by folding one part against a flat of the nut so it cannot turn
what does a shakeproof washer do
it digs into the nut
what are the common sizes of lock wire
20, 25, 30 /100 inch /gauge
what is the max number of bolts that can be wire locked together
3
when can the single wire method be used
when there is no access and it must be done in a closed geometrical shape
what are locking plates secured to
an adjacent part to the nut it locks
what are the 3 common types of quick release fasteners
dzus, airloc and camloc
what are quick release fasteners
fastened and released in a 1/4 turn
what are rivets
a fastener put into a pre drilled hole and deformed to join materials together
what is the definition of a rivet
any type of fastener that obtains clamping action by one end being mechanically upset
what type of rivet is AN426 and MS20426
a counter sunk head
what type of rivet is AN470 and MS20470
a universal head rivet
what parameters must be met before driving a rivet
the rivet must extend the base by 1.5x the original diameter
what parameters must be met after driving a rivet
the end must have expanded 1.5x the original diameter and must extend the base .5x the original diameter
what does each part of the rivet code represent
the first part is organisation and head style. the second part is the alloy material. the third part is the diameter in 1/32 inch. the last part is the length in 1/16 inch
what is classified as the length of the rivet
whatever goes into the hole
what is a friction lock rivet
a rivet that is only held in by friction of a centre bar
what is a mechanical lock rivet
a rivet that is held in place through a centre bar that is locked into place
how are friction and mechanical lock rivets removed
first removing the lock collar by punching the centre stem and then drill it out otherwise it would just spin
what are the 3 types of lockbolt used
pull type, blind type and stump type
how does a high lok bolt work
it has a shear collar that comes off when tightened leaving the locking collar behind. it also is drilled through an interference fit hole
what is a hi lite
works the same as a high lok but is made of lighter materials
what is a taper lok
the more it gets tightened the more stress it applies on the hole which strengthens the material around it
what is a hi-tigue
a fastener designed to reduce fatigue by putting radial force around the hole which pre loads it with stress making it less likely to break under fatigue stress
what are the characteristics of a square thread
very powerful root ideal for power transmission
what are the characteristics of a ACME thread
easier to cut than a square thread and also considered stronger
what are the characteristics of a buttress thread
designed to handle heavy forces in one direction
what are the 4 common types of key
woodruff, square, pratt and whitney key, gib head key
what 2 types of key are unable to move once placed in the part
woodruff and pratt and whitney
