Specification section3.3

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 fittingsScrews

HingesDowel joint

Barrel nut and boltCam fitting

T nut and boltCorner plate

Chipboard fastenerBlock connector

3.3 Joining methods (temporary): Knock down fittings

Screws 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.

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.

This shows a screw used as a knock-down fitting.

3.3 Joining methods (temporary): Knock down fittings

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.

Hinges are flexible joining fittings and can be made from steel, brass or nylon.

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.

Hinges

3.3 Joining methods (temporary): Knock down fittings

Dowel jointThe 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 boltThe 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.

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.

These type of fixtures can be undone.

3.3 Joining methods (temporary): Knock down fittings

T nut and boltAs 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

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.

Screw Screw

Wing nut

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

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.

Screws holding the first block in place.

This is the screw that can be done up and undone when needed.

3.3 Joining methods (temporary): Knock down fittings Advantages of uses

knock-down fittingsFor manufactures • For consumers

3.3 Joining methods (temporary): Knock down fittings Disadvantages of uses

knock-down fittingsFor manufactures • For consumers