3.4 joining techniques Flashcards
types of adhesives:
a
contact adhesive
rubber-based and can be made from natural or synthetic rubbers. Once the adhesive is touch dry the two surfaces are then secured with some pressure and
the bond is immediate.
acrylic cement
Dichloromethane works by dissolving the surface of hard plastics. Generally, it is used for edge glueing.
epoxy resin
The Epoxy resin sets when equal amounts of resin and hardener are mixed together. It then chemically sets to form a very hard material.
PVA (Polyvinyl acetate)
PVA works when it soaks into the surface of the wood and sets once all the water is absorbed.
Hot melt glue
Works by heating a stick of glue which resets when cool forming the bond. The glue is a kind of thermoplastic.
Cyanoacrylate
(superglue)
They provide instant bonding, clear bond lines, and cures in seconds.
PS cement
The product works by melting the plastic on application and ‘welding’ two glued pieces of plastic together
contact adhesive
materials
advantages
disadvantages
a
All Veneers, Plastic, laminates adv Adhesion takes place as soon as the two surfaces are placed together. No clamping required Multi-material.
disadvantages There is no opportunity to reposition the pieces. Relatively expensive Contains VOCs
acrylic cement
materials
advantages
disadvantages
a
Acrylic
HIPS
ad
Rapid bonding of
acrylics
disadvantages Difficult to apply Difficult to give a neat joint Relatively expensive Contains VOCs
epoxy resin
materials
advantages
disadvantages
a
all
ad High strength bonds Versatile Excellent chemical and heat resistance
disadvantages Expensive Reaches full strength only after a few days Requires manual mixing of two elements (resin and hardener) Can be messy
PVA (Polyvinyl acetate)
materials
advantages
disadvantages
a
Wood
Fabric
Styrofoam
ad Gives a strong joint Relatively inexpensive Water-based
disadvantages Surfaces need to be securely clamped together for a long period of time (24 hours) Generally not waterproof
hot melt glue
materials
advantages
disadvantages
a
Model making Any materials
ad Range of colours Good bond for models Quick to harden
disadvantages Not great for final models Safety issues with hot glue
Cyanoacrylate
(superglue)
materials
advantages
disadvantages
a
Industrial Medical Home use All materials
ad
Stong
Fast-acting
disadvantages
Short shelf life
Skin contact
ps cement
materials
advantages
disadvantages
a
Model kits HIPS ABS
ad
Strong bond
Can use a brush to
apply
disadvantages
Relatively
expensive
Contains VOCs
mechanical joining methods
b
screws
Screws are often one part of a temporary joint.
nuts and bolts
Nuts and bolts are usually manufactured from low or medium carbon steel.
rivets
Riveting is a method of making a permanent joint in metal.
screws
machine screws
b
Machine screws have parallel sides with
standard threads cut into them. They are usually
made from carbon steel and are mass-produced. They come with a variety of heads,
the most common being countersunk and
cheese heads.
screws
wood screws
b
Wood screws are classified firstly by the shape of
the screw head and secondly by the length of the
screw itself. They come with three different types of
head, countersunk, raised and rounded.
nuts and bolts
nuts
b
Specialist nuts are used for particular situations.
The advantage of using nuts and bolts is that they can be easily undone, allowing for components to be replaced or repaired.
nuts and bolts
bolts
b
The most commonly used thread form is the ISO metric
thread. The other measurement that is often
quoted when discussing threads is the pitch. The
pitch of the thread is the distance that a screw or
bolt with travel through one revolution.
rivets
solid rivets
b
Solid rivets are manufactured from soft iron
because they need to be ductile and easy to
work as they have to be hammered into shape.
rivets
pop rivets
b
Pop rivets are usually manufactured from
aluminium and instead of being hammered into
shape, they are fixed into place using a pop rivet
gun.
heat joining methods
c
Oxy-acetylene welding
MIG welding
Brazing
Hard soldering
soft soldering
Oxy-acetylene welding
c
Oxy-acetylene gas welding is commonly used to permanently join mild steel. A mixture of oxygen and
acetylene, burns as an intense/focussed flame, at approximately 3,500 degrees centigrade. When the
flame comes in contact with steel, it melts the surface forming a molten pool, allowing welding to take
place. A filler rod of the same material is often used to complete the joint.
uses a steel filler rod to create the weld
mild steel sheet, tube or plate
MIG Welding
c
MIG welding involves a process where
using an electric current, an arc is struck between the work and an electrode and this is used as the
heat source. The filler is in the form of a thin wire and as the welding progresses the wire is gradually
fed into the joint. During the operation, a flow of inert gas, usual argon, is made to flow over the area
being joined.
uses an electrode wire with an inert gas such as CO2 or argon
climbing frames, bike frames, vehicle exhausts
Brazing
c
The joint area must be cleaned up with emery cloth. Then a flux is applied to the area where the join will be. Flux serves two purposes. Firstly, when the steel is heated up, there is a reaction between the oxygen in the air and the metal. This causes oxidation, preventing the molten spelter from flowing. Secondly, the flux
breaks down the surface tension on the molten spelter and allows is to flow.
uses a brass filler rod using either oxy-acetylene or gas compressed air brazing hearth
thinner gauge, mild steel tube or bar
hard soldering
c
Hard soldering is a general term for silver soldering, the parent metal does not become fused or molten and that the filler alloy has to have a lower melting temperature range than the metals being joined. The melting temperature of hard solder ranges from 625°C to 800°C.
soft soldering
c
In many respects, this operation is similar to brazing in that the base is not melted, but is merely tinned
on the surface by the solder filler metal.
uses a filler rod to flow between the metal surfaces to create the join
copper or brass
copper piping in plumbing, jewellery and brass musical instruments
what are the main two categories of joints?
d
traditional wood joint
knockdown fitting
traditional wood joints
d
butt joint
dowel joint
housing joint
mortise and tenon joint
dovetail joint
comb joint
half-lap joint
housing joint
d
framework construction
cabinets
shelving
comb/finger joint
d
box construction
decorative edge joining
mortise tenon joint
d
frame constructions
tables
chairs
half-lap joint
d
simple frames
boxes
dowel joint
d
lightweight shelving
corner joining
knock-down fittings
d
connecting blocks
furniture connector nuts and bolts
Camlock fittings
define the phrase knock-down fittings
d
Much furniture is sold in flat packs. This makes it easy to transport and store. The customer then has to assemble it at
home.
connecting blocks
d
Made from Polyethylene, these are used for joining sheet materials and attaching kitchen units to the the underside of the worktop for example. Two-part blocks bolt together and so enable dismantling.
furniture connector nuts and bolts
d
Typical applications include cabinets, chairs, desks, shop equipment and tables. Furniture Connector Bolts are for use with Joint Connector Nuts or Cross Dowels. They are designed for use with self-assembly furniture and are easily applied with an Allen key.
Camlock fittings
d
Cam and Dowel fittings are commonly used to assemble flat pack furniture and kitchen cabinets. Cam and Dowel parts are used to pull together standard thickness board panels to give a hidden fixing.
