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Joining Metals
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2 Main Types
Temporary - when access will be needed at
some time in the future
Permanent - when a joint will never need to
be undone
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Nut and Bolt
Temporary fixing when
both sides can beaccessed
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Machine Screw
Temporary fixing when
access is from one sideonly
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Riveting Countersink and Round HeadRivets make a permanentfixing. Usually the head is
formed on the other side which
is the same as the original one.
Round Head rivets use a Snap
and Set to form new head, and
protect original.
If loose joints are required - insert
a piece of card between the pieces
and remove on completion
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Soldering
Soldering is the joining of pieces of metal with a different
metal which is melted between the pieces. The pieces being
joined do not melt.
2 typesSoft Soldering
Electrical
Gas
Hard Soldering Brazing
Silver Soldering
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Electric Soft Soldering
Use an electric soldering iron
Solder
Tin/Lead alloyFlux
Resin contained within the solder
Use soldering electronic components
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Soft Soldering
Use a small gas oven or blow torch and copper soldering
irons
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Soft Soldering
Solder
Tin/Lead alloy, called Tinmans Solder
Flux Zinc Chloride, separate from solder
Use
Soldering tin plate containers
copper water pipes (mostly pre-prepared and just needwarming)
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Brazing
Used to join Mild Steel (mainly)
Work is heated in the forge with a natural
gas/air flame
Solder
Brazing Rod (a brass alloy)
Flux
Borax, mixed to a paste with water, or
brazing rod dipped in powder flux
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Silver Soldering
Used to join silver or other non-ferrous metals
Work is heated in the forge with a natural gas/air flame
Solder
Silver solder -a silver alloy with a lower melting point thansolid silver
Flux
Borax, as brazing
UseUsed to assemble items that will be hallmarked. Silver solder
must contain a high percentage of silver or it will not be
hallmarked.
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Welding
Welding is the joining of metals by melting
the two pieces to be joined and fusing them
together with the addition of welding rodwhich is the same as the metal being
welded.
e.g. when welding mild steel the weldingrod is mild steel
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Different Types of Welding
Gas (oxy-acetylene)
Arc
Spot
MIG (Metal Inert Gas)
TIG (Tungsten Inert Gas)
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Oxy-Acetylene Welding
Flame is a mixture of oxygen and acetylene, supplied in gas
bottles
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Arc Welding
Uses the heat from a spark jumping between
the welding rod and work, completing a
circuit.
The welding rod is Mild Steel coated with
flux which melts as welding is done. It has
to be chipped off after.
Arc welding is becoming rarer as MIG
welding is much easier
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Spot Welding
Used to join sheet mild steel.
Does not distort the metal as it is only
heated in a small area.
Used to assemble car bodies.
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Metal Inert Gas
Used to weld Mild Steel
Welding rod is fed automatically through
the gun.
No flux is needed as the joint is protected
from the atmosphere by a shield of Inert
Gas (argon)
Much cleaner than arc welding
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Tungsten Inert Gas
Uses the same principle as MIG but the
welding rod is not fed automatically.
The tip of the welding gun is made oftungsten, and the welding rod is fed by
hand.
Used to weld aluminium and StainlessSteel.
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Now its your turn
In your exercise books
Sketch the process of forming a round head
rivet
Sketch a copper soldering iron
Describe the advantages of MIG welding
over Arc Welding
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Forming a Round Head Rivet
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A Copper Soldering Iron
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Advantages of MIG over Arc
No flux to chip off afterwards
Welding rod is fed automatically
Greater control with MIG. Arc very difficult
with a new rod, because of its length.