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Title: Metaljoining process
Description: Clear description of different methods of joining metals
Description: Clear description of different methods of joining metals
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5/11/2017
Forms a permanent bond between two joint surfaces
...
g glueing
By
Mr
...
Can be carried out at room or at a higher temp, with
or without pressure and for a period depending on
the time required for the adhesive to set (or cure)
...
Thin, delicate and heat-sensitive parts which heat methods of joining would distort or destroy can be
bonded
...
The adhesive layer provides:
◦
good seal against moisture;
◦
good thermal and electrical insulation;
◦
some flexibility of the joint
...
Most natural adhesives produce low-strength
joints with poor resistance to water and to
temp variation
...
Applications of natural adhesives are mainly
in woodworking and packaging industries
...
ii
...
iv
...
vi
...
Bonded structures are difficult to dismantle for
repair and replacement
...
Health and fire hazards when using solvent-based
fluids
...
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These soften when heated and do not change chemically when establishing
a bond
...
Available in liquid and solid form
...
Bonding carried out under heat&pressure after joint assembly,common
types:Cyanoacrylate (superglue) -establishes bond at room temp without
the addition of a catalyst
...
Joint surfaces are cleaned and a few drops of adhesiveare applied
...
Depending on conditions, the bond may be complete in as short
time as 15 seconds
...
These adhesives change chemically when the bond is established
under the action of heat, a catalyst or both
...
g metal, glass, ceramics, wood, concrete and thermosetting
plastics; also for bonding aluminium to itself and other materials in
aircraft &exposure to severe environmental conditions such as heat,
cold, humidity and chemical atmospheres
...
Liquids are generally twocomponent systems - mixed, cured by catalytic action with or
without the aid of heat
...
Film available in various thicknesses&has the advantages of easy
clean handling&that it can be cut to the joint shape
...
Most common types is epoxy- bond is obtained from the reaction of
a resin and a basic curing agent (hardener)&cured at room temp or
at an elevated temp to reduce the cure time
...
Used for assembly into previously tapped holes and are
manufactured in brass, steel, stainless steel and plastics
(usually nylon)
...
For light loading conditions where space is limited, a headless
can be used
These are some of the most versatile adhesives currently in use
...
e
...
Soften when heated &dnt change chemically when the bond
established
...
One of the most common types is:Polychloroprene rubbers
(neoprene)
They have good resistance to water, salt spray, chemicals, lubricants
and weak acids, but are unsuitable for structural applications
...
They are available under the brand names ‘Bostik’ and ‘Evo-stik’
impact
...
Manufactured in high-grade alloy steel with
rolled threads,
Used for higher strength applications than
machine screws
...
Different points are used either to bite into
the metal surface to prevent loosening or,
in the case of a dog point, to tighten
without damage to the work,
Bolts are used in conjunction with a nut for
heavier applications than screws
...
Hexagon-head bolts are used in engineering
up to 36 mm diameter by 150 mm long
...
Used for fast-assembly work
...
specially hardened to produce their own threads as they
are screwed into a prepared pilot hole, -eliminates
separate tapping operation
...
Has a grooves or flutes
to produce the cutting action-used on hard brittle
materials, especially where thin-wall sections exist, as this
type produces less bursting force
...
have a
special piercing point and a twin-start thread,
Bolt length is measured from the end of the
threads to the bottom of the bolt head
Bolt length does not including the bolt head
itself
Bolt diameter, or bolt size, is measured
around the outside of the threads
Bolt head size is the distance across the flats
of the bolt head
Head size is given in fractions, like wrench
size
◦ Common head sizes are 7/16, ½ and 9/16
◦ Common metric sizes are 8 mm, 10 mm, 13 mm
Both thread pitch is a measurement of thread
coarseness
Bolts and nuts can have coarse, fine, and
metric threads
Bolt threads are measured with a thread pitch
gauge
Two common metric threads are coarse and
fine and can be identified by the letters SI and
ISO
Do not accidentally interchange thread types
or the bolt, or the part threads will be ruined
Bolts and nuts are available in right- and lefthand threads
Turn right-hand threads clockwise to tighten
Turn left-hand threads counterclockwise to
tighten
Left-hand threads have notches or a letter “L”
stamped on them
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5/11/2017
(A) Thread pitch gauge
...
Threads
that match the gauge equal the pitch number printed on the gauge
...
Gauges can be used to tell thread, bolt or nut sizes
...
This will prevent part
warpage and damage
...
Where parts require to be removed frequently
and hand tightness is sufficient, wing nuts are
used,
...
Where thin sheets are to be joined and access is
available from only one side, rivet bushes or rivet
nuts are used
...
Body nuts are specially designed for specific holding applications
...
Washers distribute the tightening load over a
wider area than does a bolt head, screw head
or nut
...
Plain flat washers spread the load and prevent
damage, but do not provide a locking action
...
Outside diameter is produced larger than the
standard-size drilled hole into which it is to be
inserted
...
A chamfer at each end of the pin enables it to be
easily inserted in the hole, where it can be driven
home using a hammer
...
Lock nuts are a little over half the thickness of a
standard nut
...
Common types incorporate a nylon insert, either as a
small plug or as a strip along the length of the
thread
...
This provides an interference which will
resist rotation of the screw
...
solid and a liquid adhesive are mixed and
When the two threaded parts are assembled, the
micro-capsules of adhesive are broken, releasing the
adhesive, which hardens and provides a reliably
sealed and locks the thread
...
liquid thread locking -Applied as easy flowing
liquids which fill the gap between mating
threads, they cure into a strong insoluble plastic
...
Liquid threadlock is available in a variety of
strengths to suit different applications
...
e
...
Parts can be loosened
using normal hand tools without damaging
Low strength is recommended for use on adjusting screws,
countersink head screws and set screws on collars and pulleys
and is also used on low-strength metals such as aluminium and
brass which could break during dismantling
...
Available for threads upto 24mm dia- maybe
Square or rectangular section in a single coil,
with the ends of the coil raised in opposite
directions
...
In addition, the spring is flattened
during the tightening of the screw, bolt or nut,
which gives constant tension during use, Shakeproof washers are used for thread sizes up to 16
mm and can have external or internal teeth
...
Circlips are available in sizes from 3 mm to
400 mm and larger
Manufactured from high carbon spring steel
...
Wire rings or snap rings can be used as a
cost-effective replacement for the traditional
type of circlip in both internal and external
applications
A locking washer is inserted under the head
of a screw, bolt or nut to prevent it working
loose during service
...
External circlips usually fitted in a groove in a
shaft, prevents the shaft from moving in an
axial direction or prevents an item fitted to
the end of a shaft from coming loose, e
...
a
bearing or pulley
...
...
Keys and set screws are both used
to align parts on shafts
...
(B) Set screw application
◦ its speed, simplicity, dependability and low cost
...
In riveting, forming the end is
known as clinching
...
Tubular rivets are designed for application where
lighter clinching forces are used
...
These have a parallel hole
and can be used for components of varying
thicknesses
...
Riveting as a means of fastening is used because
of
Used in permanent joints as pivots, electrical
contacts and connectors, spacers or supports
...
Rivets are available in steel,brass,copper and
aluminium in a variety of types
...
The rivet shank is
intended to expand during the setting operation
in order to fill the predrilled hole in the work
...
Self-piercing rivets, have been specially
developed to pierce thicker metal and clinch in
the same operation for metal up to 4
...
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5/11/2017
Rivets which can be set when access is limited to one
side of the assembly
...
The rivet is set by inserting the mandrel in a tool
having a means of gripping, and the rivet is inserted
into a predrilled hole in the assembly
...
When the joint is tight, the
mandrel breaks at a predetermined load,
...
...
Plated steel rivets are used where low cost,
relatively high strength&no special corrosionresistance is required;
Al for greater resistance to atmospheric&
chemical corrosion
Monel for high strength&high resistance to
corrosion
...
(c) Select any three from the following materials and identify
the process used for making a permanent joint in each
case
...
(d) Give two reasons why goggles must be worn when gas
welding
...
(ii) Flux is required at the joint to remove oxides, keep the weld
pool clean from impurities and allow the weld to cool slowly by
producing a slag covering
...
(iv) Leather gloves must be worn to protect the user from hot metal
particles, UV
light and or high temperatures
...
To protect the user from bright light
produced
by the gas flame
Title: Metaljoining process
Description: Clear description of different methods of joining metals
Description: Clear description of different methods of joining metals