All screws must have pilot holes made before they can be driven home. For screws into softwood smaller than No. 6 gauge, make these with a bradawl. Drive it into the wood with its chisel point across the grain, to avoid splitting.

Screws into hardwood and screws into softwood larger than No. 6 gauge need two pilot holes. One is for the thread, the pilot hole and one for the shank, the shank hole.

For all except the largest pilot holes, use twist drill bits. Those for pilot holes should be the same size as the screw core to which the threads are attached. Those for the shanks should match them exactly.

When drilling pilot holes, mark the required depth on the drill bit with a piece of masking tape. This will tell you when to stop and helps prevent the drill chuck damaging the work piece should you over drill.

As with nailing, where two pieces of wood are to be fixed together, screw the smaller to the larger. Drill the shank hole right through the smaller piece so it is pulled down tight as the screw is driven home. If the shank hole goes

only part of the way through you will find it very hard to pull the top piece of wood down tight and may risk breaking or damaging the screw. Brute force should never be used, it indicates that either the thread hole or the shank hole is too small.

[edit] Counter Sinking & Boring

Countersinking: Countersinking is normally the easiest way of recessing screw heads flush with, or below, the surface of the wood. The recess is made with a countersink bit after the pilot has been drilled, to the same depth as the countersunk screw head. Take particular care if you are countersinking with a power drill or the recess may accidentally become too large.

Counter Boring If the wood being fixed is thicker than the length of the screw shank, drill a hole the same size as the screw head part-way through the wood, and fill the hole afterwards with a plug of wood or a length of dowel.

[edit] Drilling Techniques

Using the correct drilling technique makes all the difference to the quality of the finished work. Whether your drill is power or hand operated, you should always hold it at right angles to the work surface so that the pilot hole is straight. If you find this difficult, rest a try square upright near the bit and use it as a guide.

With twist drills, operate the drill in bursts and lift it frequently to allow debris to escape. To give yourself as much control as possible, always hold the drill with both hands and never press too hard, you are bound to over drill.Keep the chuck key taped to the cable, so it is handy whenever you want to change drills.

Using a hand-operated wheel brace requires slightly more effort, but gives more control than a power drill. When drilling vertically, grip the handle with your thumb on top. Turn the wheel steadily to avoid knocking the drill out of line. To drill horizontally, grip the handle with your thumb towards the wheel. Alternatively, where a side handle is fitted, grasp this in one hand while you turn the wheel steadily with the other.

[edit] Driving Screws

Always make sure that the tip of your screwdriver is in good condition and that it fits exactly into the slot in the screw head. A blade that is too narrow or rounded damages the slot, while too wide a blade damages the wood as the screw goes in. When using a pump-action screw­driver, hold it firmly in both hands— one on the handle, the other on the knurled collar just above the bit— and make sure that you are not off-balance. Any loss of control could cause the blade to slip out of its screw slot and damage your wood.

To make screw driving easier, the screws can be lubricated with wax or candle grease before driving. Brass screws are quite soft and to prevent damage when screwing into hard­wood, the resistance can be lowered by driving in a steel screw first.

[edit] TRADE TIPS

Q. The screws holding the shelves in my bookcase have started to loosen. What causes this ?

A. Screws do not hold well when driven parallel with the grain of the wood, that is into the end grain. You could reinforce them by using fibre wall plugs two sizes larger than normal, for example. No 8 plugs for No 6 screws and dunking the plugs in neat PVA adhesive before driving the screws.