mechanical fixing & adhesive bonding
Candidates are required to demonstrate a knowledge and understanding of the safe use of the bench tools and their component parts listed below:
Clicking the image will take you to a YouTube link to access further information about some of these tools.
NAILS
round head nail
A round head nail is mainly used for general construction work, particularly in the building industry. The head of a round nail cannot be punched below the surface of the wood.
oval brad nail
An oval brad nail is used for joinery and flooring. The shape of the shaft of the oval brad helps prevent the wood from splitting when it is driven into the wood. The head of the oval brad can be hidden below the surface of the wood using a nail punch.
panel pins
A panel pin is a small thin nail that is mainly used for fixing thin sheet material to the bottom of boxes or the backs of cabinets. Panel pins are normally used along with glue to hold a joint together while the glue is setting. To improve the finish of a piece of work, the head of the panel pin can easily be punched below the suface of the wood with a nail punch.
SCREWS & SCREWDRIVERS
Screws are an effective way of joining two or more pieces of wood together on either a temporary or permanent basis- they are only joined permanently when glue is applied. Screws are stronger, neater and more accurate than nails and can easily be removed, meaning the parts can be separated without damage.
The two most common types are COUNTERSINK and ROUND HEAD screws. You will notice that the two screws are the same basic shape, with the main difference being the shape of the head of the screw.
COUNTERSINK SCREW
The countersink screw is the most commonly used general purpose screw in the workshop. A countersink rose creates a chamfer in the entrance to a drilled hole, allowing a countersink screw head to go level or slightly below the surface of the material. As a result, countersink heads are commonly used in situations where the screw must be partially or fully concealed.
round head SCREW
The round head screw is also known as the domed head screw. The round head sits on the surface of the material unlike the countersink head. A common use for a round head screw is for attaching fittings to wood, for example, a tee hinge on a shed door or a latch on a garden gate.
procedure for driving in a screw
When driving a screw into a piece of wood, care should be taken not to split the wood. The following procedure is recommended when joining two pieces of wood.
A clearance hole, which is larger than the thread of the screw, is drilled into the top piece of wood.
Next, a pilot hole, which is smaller than the diameter of the screw, should then be drilled into the bottom piece of wood.
If the screw is required to lie flat with the surface of the wood, the top of the clearance hole should be countersunk using a countersink rose.
If you look closely at the head of a screw, be it a round head or a countersink, you will see it has a straight or cross shape. This is known as the type of drive. the end of a screwdriver is made to fit the type of drive.
SLOTTED DRIVE
A straight head screwdriver, is designed to fit into the head of a screw which has a slotted drive.
CROSSHEAD SCREWDRIVER
There are two types of cross head screwdriver, a Phillips and a Phozidriv, with the Phozidriv being the more commonly used
PHILIPS & POZIDRIV DRIVE
As you can see from the image above, the drive of the Phillips and Phozidriv both have a cross shape cut into the centre.
KNOCK DOWN FIXINGS
Many items of furniture you will find around your home such as kitchen cabinets and wardrobes have been designed so that they can be joined together or taken apart quickly and easily at home. This type of self-assembly furniture is known as flat-pack furniture as is commonly made from manufactured board and joined together using various mechanical fixings known as knock down fixings. Some commonly used knock down fixings are shown below.
CORNER BLOCK
A corner block is one of the most basic knock down fixings used in self-assembly furniture. It provides a strong, cheap and effective method of joining 2 pieces of wood together at right angles. Although the example in the picture shows a plastic corner block, it could quite easily have been made from a piece of natural timber such as pine.
BARREL AND BOLT JOINT
A barrel and bolt joint is one of the strongest knock down fixings and can be taken apart and reassembled quickly and easily. Typically found in self-assembly tables, the barrel and bolt joint is assembled by inserting the bolt through both components to be joined together where it locates the threaded hole in the barrel, and it is tightened by allen key.
CAM LOCK FIXING
One of the strongest, most complex knock down fixings is the cam lock fixing. Commonly found in self-assembly kitchen cabinets, this fixing uses a specialist screw which is tightened into one component then inserted into the second component where the head of the screw is located in the cam. the cam is then tightened by a screwdriver, which in turn pulls the two componenets together.
FURNITURE SCREW CONNECTOR
A basic and easy to assemble and disassemble knock down fixing is the furniture screw connector. As the name suggests, this is commonly used in the assembly of flat-pack furniture. Its deep thread provides an accurate, close-fitting joint in the manufactured board where normal wood screws could easily tear out.
ANGLE BRACKET
Angle brackets are commonly used as structural support for reinforcing right-angle corner joints. It's a simple method of joining materials together, and just like the corner block it is held in position using screws, meaning it can be taken apart and reassembled quickly and easily.
WOOD ADHESIVE
Unlike knock down fixings, traditional wood joints are assembled using wood glue. The most commonly used wood glue in schools is PVA glue. PVA (polyvinyl-acetate) glue is a thick, white water-based glue. Unlike superglue, which has a very short setting time, PVA will take around 3-4 hrs to dry and set to a strong, permanent joint.
ADVANTAGES OF FLAT-PACK FURNITURE
Self-assembly furniture which is joined together using knock-down fixings has many advantages over traditional woodworking techniques:
It's cheaper to manufacture as consumers assemble it themselves.
It's made from manufactured board, rather than natural timber, which is better for the environment.
It's quick and easy to assemble and take apart using limited key equipment - often just a screwdriver or Allen Key is required.
It's easier to transport and deliver; for example large furniture items such as wardrobes and dining room tables, which are awkward to handle and manoeuvre around a house when they're assembled, can be assembled in the room where they will be used.
THINGS TO DO AND THINK ABOUT
State two advantages of using knock down fixings rather than traditional woodworking joint techniques.
State the name of the screw which a straight head screwdriver is designed to fit into.
Explain how to ensure the head of a screw lies level with the surface of material.