Screws & Glues

Question on identifying types of nails have appeared in past examination papers.

COUNTERSUNK - SLOT HEAD:This can be used for general woodworking for example fitting hinges to doors. Because the screw is countersunk it can be tightened 'flush' to the surface of the material.







POZIDRIV HEAD: Used with special screw drivers which will not slip when pressure is applied. This is ideal when using screws in corners or confined spaces.

Round Head Screw : These are used for fixing pieces of material together where countersunk holes are not being used. Round head screws can look quite decorative especially if they are made of brass.



Difference between round head and counter sunk screws is that counter sunk is triangular (more like a funnel therefore deriving the word 'sunk' or a pyramid) and round head is circular, hence the name round head screw (see images above to compare them)

Plastics can be joined using a range of modern glues:

Perhaps the best glue is Tensol Cement which joins plastics such as perspex together permanently. The glue is applied to the surfaces to be glued and they are pressed together. They should be clamped for 24 hours and this gives a permanent joint. Contact adhesive can be used to join plastics. The adhesive is applied to both surfaces and when the surfaces appear to be dry they are pushed together. If the two pieces of material are left for a number of hours, they are virtually impossible to take apart. Many adhesives are plastics themselves. A good example is ‘Araldite’ which is an epoxy resin that hardens when a second chemical is added (called a catalyst). It can bond most materials including some plastics. The two tubes can be seen in the diagram. An equal amount of each tube are mixed together and then applied to the material to be glued. Super glue (cyanoacrylate)is another adhesive that joins plastics together, very quickly. Great care must be taken when using this type of glue as it will just as easily glue fingers together. For this reason super glue is not used in schools.   A glue gun can be used to join a variety of plastics. This glue usually gives a semi-permanent joint as surfaces glued together can sometimes come apart. The glue is a type of plastic that melts when hot and solidifies when it cools. Be careful to select that right type of glue stick - this depends on the material to be glued. General purpose glue sticks are usually used in schools.