Specification section
3.3
3.3 Joining methods (temporary): Knock down fittings
What you need to learn
The advantages and disadvantages
of using the various knock down
fittings when joining materials and
components.
3.3 Joining methods (temporary): Knock down fittings
What are 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,
Allen key 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.
• They are known as ‘component parts.’
3.3 Joining methods (temporary): Knock down fittings
The different types of fittings
Screws
Hinges
Dowel joint
Barrel nut and bolt
Cam fitting
T nut and bolt
Corner plate
Chipboard fastener
Block connector
3.3 Joining methods (temporary): Knock down fittings
Screws
When using screws,
you will need to drill a
pilot hole before
screwing the screw into
the material. This
helps to guide the
screw into place, but it
must not be so big that
the thread doesn’t grip
to the material.
Countersunk head machine
screws, also called set screws.
Set screws are also called
machine screws. They have a
thread that goes right up to the
head.
Self tapping screws are made of
hardened steel and cut their
own thread as they are screwed
in. A tapping size hole equal to the
core diameter of the screw should
be drilled before the screw is
inserted. They are used for joining
thin sheets of metal and plastics.
This shows a screw used as a
knock-down fitting.
3.3 Joining methods (temporary): Knock down fittings
Hinges
Hinges are flexible joining fittings and can be made from steel, brass or nylon.
Concealed hinges are strong spring loaded hinges that
can be adjusted once the hinge has been fitted. They are
often used on wardrobe and kitchen cabinet doors.
Butt hinges are usually let into the edges of doors and
frames so that they are almost hidden from view when
the door is shut. Cupboard and room doors, lids of small
boxes and windows.
Piano hinges are long butt hinges. They allow the
screw
holes to be spread along the whole surface of the door to
give extra holding power. This is useful when attaching
hinges to edges of man made boards. Piano hinges can
be cut with a hacksaw to the required length. They can
be used on pianos and box and furniture lids.
3.3 Joining methods (temporary): Knock down fittings
Dowel joint
The dowel joint is basically the same as a butt
joint except dowels are used to hold the two
pieces of wood together instead of screws and
nails
It is important that the holes are aligned
correctly otherwise the joint will not be
square.
You can leave the joints so that they are not glued
if you wanted to take them apart or glue will make
the joint stronger but also permanent. By using
dowels that have indents, it increases the gluing
area. They are not a knock-down fitting if you
glue it.
If used as a knock down fitting you would also use a screw.
3.3 Joining methods (temporary): Knock down fittings
Barrel nut and bolt
The nut is placed in the wood
with the hole in it facing the
bolt. The nut has a thread
inside it.
When you do up the screw the
end of it will find the hole in the
nut. You keep the nut in place
with a flat-headed screw driver.
3.3 Joining methods (temporary): Knock down fittings
Cam fitting
You will need to line the plug with
the cam fixture.
These type of
fixtures can be
undone.
Use a Philips head screw driver to
turn the cam fixture once the plug is
in place and the wood has butted
together. This will lock the plug in
place.
3.3 Joining methods (temporary): Knock down fittings
T nut and bolt
As the bolt is done up, the t
nut grips into the wood. As
there are three prongs on the
nut, it stops the bolt from
undoing.
T nut
3.3 Joining methods (temporary): Knock down fittings
Corner plate
Wing nut
Screw
Screw
The two screws connect the plate to the side. The wing nut in the
centre allows you to join the plate to the corner and do it up tightly.
3.3 Joining methods (temporary): Knock down fittings
Chipboard fastener
Rawl plug
Screw
As the screw thread
would not be able to
grip inside the
chipboard, a rawl plug
is placed inside the
hole. This allows the
screw to grip onto
something and as the
screw is screwed into
the plug, it expands
and allows the screw to
make a strong joint.
3.3 Joining methods (temporary): Knock down fittings
Block connector
Screws holding the first
block in place.
This is the screw that
can be done up and
undone when needed.
This fitting allows a piece of furniture to be taken
apart without the need to remove all screws. This
is particularly important in chipboard constructions
as repeated screwing into chipboard will quickly
result in stripped threads and reduced holding
power.
3.3 Joining methods (temporary): Knock down fittings
Advantages of uses
knock-down fittings
For manufactures
• For consumers
3.3 Joining methods (temporary): Knock down fittings
Disadvantages of uses
knock-down fittings
For manufactures
• For consumers