Fasteners Flashcards
functions of fasteners
join components together
constrain relative movement
transmit forces between components
general classifications of fasteners
permanent fasteners
removable fasteners
reusable fasteners
non-reusable fasteners
key functions
transmit torque from shaft to gear (or vice versa)
prevent relative rotation
types of keys
square key
flat key
gib head
Pratt & Whitney key
woodruff key
advantage of a flat key
allows for space constraint
why the hell are gib head keys like that?
they’re driven into position
advantage of Pratt & Whitney key
avoids stress concentrations
advantage and disadvantage of woodruff key
can tilt in the keyseat - easier assembly
more complex to machine
‘rule of thumb’ for deciding key width
make key width 0.2d - 0.25d where d is the diameter of the shaft
then adjust length to get desired stress levels
most common manufacture method for keyseats
end milled slot
what manufacture method should you use to get a keyseat with squared corners?
plain milling
what form of milling can be used to avoid a radius?
none
how are keyways cut?
broaching
when are splines used?
very high torque applications
applications where we want to permit some axial sliding
alternatives to keys
solid axial pin
solid transverse pin
spring/expansion pin
type of fit required for a solid axial/transverse pin
press fit
advantage of spring pin
fit is less critical
pin function
stops the thingy sliding off the whatsit
basic steps of rivet installation
hole drilled through both parts
rivet inserted into hole
rivet head gets deformed
advantage of rivets
unlikely to loosen (require plastic deformation)
why are large rivets heated before deformation?
to soften them
cooling causes shrinking which creates a preload
a ________ is used to deform the head on a pop rivet
internal madrel
type of fastener used for axial location
circlip (/retaining ring)
circlips cannot be reused if they have been ________
plastically deformed
basic operation of a snap fit fastener
head of clip is shaped to deform on insertion
clip ‘snaps’ into position after passing the locking feature
advantage of a snap fit fastener
no tools required for assembly
any deformation involved in the insertion of a snap fit much be ______
elastic
what type of material is better suited for snap fits, and why?
polymers
low modulus = large elastic deformation
