Wood Fastenings

NAILS

Nailing is a fairly strong, cheap and quick method of fastening wood.

Nails have a head, shank and point and are usually made from mild steel wire. Galvanized, copper-plated or aluminium nails are used for work which will be in contact with water.

In Rural Building we use mostly wire nails. We group these into two classes: wire na 's with flat heads and wire nails with very small heads, known as lost head nails. Some nails are used for special purposes, like staples, concrete nails and roofing nails.

WIRE NAILS WITH FLAT HEADS:

These are nails with large flat heads (Fig. 1). The head prevents the fastened member from being pulled off over the head of the nail.

These nails are available in sizes from 7 to 310 mm long.

WIRE NAILS WITH SMALL HEADS (LOST HEAD NAILS):

These are wire nails with vwry small heads which can be punched or set below the surface of the wood and covered with putty. The disadvantage of this nail is that the nailhead can be easily pulled through the wood, so it cannot be used for heavy construction work (Fig. 2).

These nails are available in sizes from 7 to 100 mm long. Small lost head nails are called panel pins.

CONCRETE NAILS:

These are hardened steel nails, available in different shapes and sizes. They are used to fix things to concrete or masonry (Fig. 3).

STAPLES:

These are U-shaped nails (Fig. 4) with two points. They are used to fasten wires and screens to walls or timber.

ROOFING NAILS AND WASHERS:

Special roofing nails are used for fixing corrugated sheet materials. They should be aluminium or galvanized metal to prevent rust, which could cause the nailhead to break off. The nails must be long enough to go at least 2 cm into the wood.

Drive screws, or screw nails as they are sometimes called, are commonly used for roofing (Figs. 5 & 6) and they have largely replaced nails with plain shanks (Fig. 7). The drive screws are galvanized and the 3hank is 2 mm or more in diameter, with a steep thread around it.

Drive screws can be driven in with a hammer, but they are very difficult to pull out again.

There are different types: either with a metal washer already attached to the head of the nail (spring head roofing nail, Fig. 6), or with loose metal washers (Figs. 5 & 7)

The washers or the spring heads prevent the nails from being pulled through the roofing sheet. They should be thick and wide enough (at least 2 cm in diameter) so that they secure the sheets well.

Roofing felt is always used under the washer to prevent leaking. The felt should be larger in diameter than the washer. Place the washers correctly: the hollow side should face the roofing felt and the sheet.

ORDERING NAILS

When ordering nails, state the kind of nail; the thickness (in 1/10 mm) and the length (in mm). Also state the material of the nails.

Example: Lost head nails; 16 x 30; steel

SCREWS

After nails, screws are the next most common type of wood fastener used in Rural Building. Screws are superior to nails because:

• they have greater holding power,
• they cause less shock to the work when driven into it,
• and they are easily removed, without damage to the work.

Screws are made of mild steel, brass, copper or they are galvanized. Usually mild steel screws are used because they are stronger than the copper or brass ones.

The parts of a screw are: the head (a), the slot (b), the shank (c), the thread (d), the point (e) and the core (f) (Fig. 1).

Screws are classified according to the shape of their heads:

• Countersunk head screws (Fig. 1)
• Round head screws (Fig. 2)
• Raised countersunk head screws (Fig. 3)
• Coach screws (Fig. 4).

Posidriv or Phillips screws have a head which is not slotted across the full width like common wood screws. They have a cross-shaped recess into which a special screwdriver fits.

COUNTERSUNK HEAD SCREWS:

The head of this kind of screw is flat on top and tapering underneath. The length is measured from the point to the top of the head (Fig. 1).

These are general purpose screws, used where the head of the screw must be flush with or below the surface of the wood.

ROUND HEAD SCREWS:

The head of these screws is round on top and flat under-neath, and the length is measured from the underside of the head to the point (Fig. 2, page 210).

These are used only where the head can be visible and can project above the surface of the wood, and when fixing light metal, where the metal is too thin for counte rsinkiug.

RAISED COUNTERSUNK HEAD SCREWS:

The head of this screw combines the round and countersunk heads; round on top, tapering underneath. It is stronger than the round head screw because the head is lest likely to break off. The length is measured as indicated in Fig. 3.

These screws are used in fixing heavy fittings and thick sheet metal, where strength is needed.

COACH SCREWS:

This is a strong screw with a square head. Unlike other wood screws, it is turned with a spanner. Always put a metal washer under the head to prevent damage to the wood surface. The length is measured from the point to the underside of the head (Fig. 4).

These are used for heavy construction work, for gate hinges, carriage work etc, where the head doesn't interfere.

ORDERING SCREWS

Screws are sold by number or in boxes containing a gross (144 screws). When ordering screws state the following in the order:

• thickness in mm
• length in mm
• kind of screw
• land of metal
• amount needed

For example: 3 x 30; roundhead; brass screws; 3 gross or, 5 x 50; coach screw, mild steel with washers; 2 gross.

BOLTS AND NUTS

Bolts and nuts are yet another means of fastening two pieces together. Bolts have hexagonal heads and are tightened up with the nuts. Bolts and nuts are used for heavy construction work (Fig. 1).

If bolts are used in timber, washers must be laid under the nut to prevent it from sinking into the wood (Fig. 3).

COACH BOLT

These bolts have oval heads and a square shank just under the head. This is so that the bolt grips the wood and doesn't turn when the nut is tightened up (Fig. 2).

The advantage of these bolts is that the head doesn't project up, since it is rounded and pulled into the wood.

WASHERS

A washer must always be used under the nut with both coach and regular type bolts. Never put a washer under the head of a coach bolt.

Washers can be made locally from a square piece of metal with a hole drilled in it.

SPRING WASHER

To prevent the nut from loosening when it is fastening metal to metal, a spring washer can be put between the metal and the nut. (Fig. 4).

ANCHORS

Fastening wood or other materials to concrete or masonry can be a problem. Often a screw will not hold in a landcrete block, or will not grip in concrete. Anchors can be used to solve this problem.

Anchors can be classed in two groups:

• anchors fixed during the initial construction
• anchors which are fixed after the initial construction.

The first type of anchor can be an iron rod set into the wall during walling or casting, as is often done with the door frames. Threaded iron rods can be used, to receive a nut later (Fig. 1).

Another way is to insert wooden blocks in the masonry; into which screws, etc. can be driven later. For maximum strength the wooden block should be dovetail shaped (Fig. 1) and it should be cut and fixed in a way that its shrinkage will have as little effect as possible on the wall.

The second group are the devices used to fix a piece to an already existing masonry or concrete work. The most simple of these is a wooden plug. A hole is chiselled or drilled into the masonry and into that hole is inserted a cylindrical plug of wood, which has the same diameter as the hole. The length of the plug should be a little less than the depth of the hole. The plug is made out of hard dry wood and the end which enters the wall is chamfered to enter smoothly. When a screw is driven into the plug, the wood will expand or even crack and the screw is wedged into position (Fig. 2).

More complicated devices, all sharing the same principle of holding a screw or nail by expanding, are now available. The most common one is a plastic plug (Fig. 3).