Joining
Techniques
Wood, Metal and Plastic
Design and Manufacture
How to join Wood….
• There are 4 main ways to join wood; an
adhesive, a joint, a nail or screw or using
a knockdown fitting. Common wooden
products that you use every day will
incorporate some of the joining techniques
above.
Gluing
The majority of the
time Polyvinyl
acetate (PVA)
wood glue will be
used to join wood.
PVA glue is used in
the workshop
every day and is
the glue you would
use to make paper
Mache.
Nails and screws
• There are many types of nails and
screws to fit your needs. Some
common ones are below.
Round head
Oval head
Countersink or
flathead
Knock-down fittings
• Knock-down fittings are
those that can be put
together easily, normally
using only a screw driver, a
drill, a mallet/hammer and
other basic tools. They are
temporary joints although
many are used to
permanently join together
items such as cabinets and
other pieces of furniture
that are purchased in a flat
pack.
Other glues that could be used would be
Superglue, epoxy resin, Hot glue, and a
number of different resin glues; Phenol
formaldehyde resin, Urea-formaldehyde
resin.
Before these modern glues the glue of choice was
animal glue or hide glue. It is manufactured from
rendered collagen from the skins (hides) of
animals. It is chemically similar to edible gelatine
and is non-toxic if ingested. Hide glue is still used
today in specialized applications: musical
instruments (lutherie), for replica furniture, and
for conservational-grade repairs to antique
Wood joints
Butt Joint
The most simple and easiest to make
wood joint is the Butt joint. The joint
relies solely on the strength of the
glue to hold it together.
Housing Joints
What is a Housing joint?
• Housing joints are used when two pieces meet at
right angles on their narrow face. A shallow trench is
cut across the grain of the vertical member, the shelf
or panel is then glued into a simple straightforward
housing and all the loads are transferred to the sides
of the unit. Pins can further strengthen the joint.
What are the advantages of this type of joint?
•
Simple to make.
•
Strong.
•
In its basic form only one component has to be
shaped.
What are the applications for this type of joint?
• Used for fixing shelves to vertical panels in deep
cabinets, bookcases, storage units and boxes, or for
drawer fronts and carcase/frame construction.
Types of Housing Joints:
Through housing joint
The trench of the though housing goes
fully across the piece of wood so the
joint can be seen.
Stopped housing joint
• For decorative effect, the trench of the
housing is often stopped short of the front
edge of the side panel by some 9 - 12
mm. No part of the joint is visible from the
front because the joint is completely
concealed. This is particularly important
where a high quality finish is required.
Mortise and tenon joints
What is a Mortise and tenon joint?
• The mortise and tenon is one of the most common joints used by
woodworkers and is the traditional corner joint for sturdy frames.
What are the advantages of this type of joint?
•
Neat and very strong.
•
Large surface area for gluing.
•
It cannot wobble.
•
Is difficult to pull out.
•
Most of the joint is hidden in the timber.
What are the disadvantages of this type of joint?
•
Can be fairly difficult to mark out and cut.
•
Poor resistance to tension, especially if badly fitted.
What are the applications for this type of joint?
• Used where maximum strength is important in window, door, chair,
mirror, bed and table frames and frame-and-panel cabinets or
external work like garden or street furniture (seats, tables etc)
Through mortise and tenon joint
In a through mortise and tenon joint the end
grain is visible and the joint needs accurate
cutting for good appearance.
Haunched mortised and
tenon joint
In order to include a strong joint at the frame, a
haunch is introduced to the joint. The haunch
prevents the frame from twisting and makes it
firmer, giving it added strength. It also increases the
gluing area.
Stopped mortise and tenon joint
This is the best joint for external work as most of the joint is
protected from the weather by tenon shoulders. The joint is
strong and concealed and used in furniture construction where a
high- quality finish is required.
The stopped mortise and tenon joint is a good looking joint
because the tenon of this joint does not show on the outside face.
The depth of the mortise should be three-quarters of the
thickness of the wood being joined.
Dovetail
What is a Dovetail joint?
• Dovetails are the strongest of all joints. The joint is made
up of interlocking wedge-shaped elements called pins and
tails that resist the forces applied to the joint. This joint
looks attractive and, if well made, the decorative quality
can be used to enhance projects. In other projects the joint
can be hidden completely. Dovetail joints work best when in
tension. For example, the most common application of the
dovetail joint is in drawer making as the strength of the
joints tails and pins resist the pulling forces applied to the
drawer. Dovetails are so strong it is rare to see a drawer
that has broken as a result of joint failure, even when put
under frequent stresses.
Finger joint
A finger joint or comb joint is a woodworking joint
made by cutting a set of complementary rectangular
cuts in two pieces of wood, which are then glued. To
visualize a finger joint simply interlock the fingers of
your hands at a ninety degree angle; hence the
name "finger joint." It is stronger than a butt or lap
joint, and often contributes to the aesthetics of the
piece.
Other common wood joints
Lap joint
T joint
Dowel joints
How to join Metal….
• There are a number of ways to join
Metals. Some common joining
techniques are, rivets, adhesives and
thermal joining.
Women riveting
the side of an
airplane panel
at Ford Motor
Company’s
Willow Run
bomber
assembly plant
in Ypsilanti,
Michigan,
August 23,
1944.
Riveting
Rivets are used to join plates together and they have
been used for hundreds of years. Before the
widespread use of welding, rivets were used in
heavy industries such as ship building. The steel
plates used to build ships such as the Titanic and
the naval Dreadnaughts of World War One were
held together by steel rivets. Rivets have largely
being replaced by techniques such as welding and
brazing. However, joining plates together with
rivets is still a useful technique especially if the
plates to be joined are quite small.
Cold rivets are still used in school workshops
although the modern pop-riveting technique is
more popular.
Riveting
video
Adhesives
Glues like in wood can also be used
with metals. Glues like the epoxy
resin can also be used to glue
together sections of metal.
Thermal joining
• Thermal joining means using heat in
order to join metal together. Some
methods of joining metal together
using heat are welding, soldering and
brazing.
Arc Welding
Arc welding is a type of welding that uses a welding power
supply to create an electric arc between an electrode and the
base material to melt the metals at the welding point to create a
permanent joint.
Brazing
Brazing is a metal-joining process whereby a filler
metal is heated above melting point and
distributed between two or more close-fitting
parts by capillary action. The filler metal is
brought slightly above its melting temperature
while protected by a suitable atmosphere, usually
a flux. It then flows over the base metal (known
as wetting) and is then cooled to join the work
pieces together. It is similar to soldering, except
the temperatures used to melt the filler metal are
higher for brazing.
Soldering
• Soldering is a process in
which two or more metal
items are joined together by
melting and flowing a filler
metal (solder) into the joint,
the filler metal having a
lower melting point than the
adjoining metal. Soldering
differs from welding in that
soldering does not involve
melting the work pieces.
Soldering is commonly used
in electronics to create
circuits.
Soldering video