Most candidates were able to:

• name types of wood screws;
• sketch the screws;
• label the parts of the screw;
• state the advantages of plywood over solid wood.

However, they were unable to explain the given gluing terms (shelf life, pot life and cramping time).  The expected response to question 3 is as given below:

(a)        (i)         Types of wood screw are:
                        -  countersunk head screw;
                        -   raised head or oval screw;
                        -   round head screw;
                        Philips head/Podzi drive screw/star head.
            (ii) Sketch of the screw

 

(b) Advantages of plywood over solid wood

-           Plywood is more uniform in strength than solid wood.
-           Plywood is more economical than solid wood in the use of valuable wood.
-           It is easier to bend plywood than solid wood for curved work.
-           Plywood is more durable than solid wood.
-           Plywood can be obtained in larger sheets than solid wood.
-           Plywood can be nailed at the edges without splitting while solid wood cannot.

(c) Explanation of Gluing Terms

• Shelf Life

It is the length of time a glue can be stored between manufacture and mixing for use before it deteriorates due to slow chemical action.

• Pot Life

It is the length of time the glue can remain usable after mixing.

• Cramping Time It is the length of time a job should be left in the cramps before it can be safely removed.