Hardware and fittings

Identify and select appropriate fittings and allied materials to use in practical projects

Select and competently use the most appropriate hardware items in the Major Project

Screws

A screw turns its way into wood by means of a spiral thread. Although Archimedes is credited with having invented the spiral about 250 BC, and wooden screws for screw presses have been in use for hundreds of years, it was not until the nineteenth century that a way was found to make metal screws quickly and cheaply enough to bring them into general use as fasteners.

Look at Figure 1 below and note the various parts of a screw, and their names. More modern styles of wood screw are now available that have parallel threads and shanks, which are less prone to splitting the timber and only require one size hole if pre-drilling. Some screws are even produced with their own drill-shaped tip so they can go through a steel roof in to timber.

The choice of screws is bewildering because specialist screws are being produced for virtually every purpose. Some have steeper spirals (for quicker fixing) or coarser threads (better holding ability-as in particle board). There are screws with twin threads, screws that are totally threaded all the way to the head and even screws with special heads like 'bugle' for plasterboards.

Size

Length is measured from the screw tip to where the screw will finish at the surface of the timber. For example, a round head sits above the surface and is measured to the flat underside of the head but a countersunk head is measured over its total length because it ends level or beneath the surface of the wood.

Figure 1. Details of wood screws. Note 'length' is only that part of the screw that is inserted in the wood

The diameter (D), or gauge to be correct, is measured at the shank just under the head.

What is a shank?

The shank is the smooth portion of a wood screw which has no thread and begins immediately beneath the head.

The measurement used is slowly changing to millimetres but some are still sized by a gauge number (from 1 to 20-the larger the number, the fatter the shank) As the length increases, so does the gauge in order to maintain strength.

The top (approximately 30%) of the shank is unthreaded because when two pieces of timber are joined together, the first piece is a clearance size so the screw just pushes through and is stopped by the head. Threading only occurs in the second piece, which finally draws the top piece tight via the head pulling it down.

Head shape

There are four common types of head shape for wood screws: countersunk, round head, raised/ countersunk (more simply called 'raised') and coach. There are other heads, like pan head, which have evolved for a specific use.

Countersunk heads are for sinking below the surface of timber and filling with putty, a timber plug or a plastic cap.

Round heads are used to pull an upper surface down to a base; for example, a plastic fixed lid. Note: The plastic hole must be shank clearance size so that the screw just drops into it but the head prevents it going right through.

Raised heads are used with a surface-mounted or recessed screw cup for situations where regular removal might be necessary. The screw cup prevents damage to the wood and enhances the appearance of an otherwise plain screw head.

Coach screws are a square or hexagonal headed screw, normally of a large gauge. These are used to screw down machinery to wooden floor joists and are tightened with spanners (see Fig. 1).

Methods for tightening wood screws

Straight slotted, Philips (four points), Pozidriv (four points plus four smaller points in between, it also has a scribed cross on the head for recognition), clutch head (vandal proof-only works in tighten direction). There are different sizes of all the types of screwdrivers to match the head slot of the screw. There are at least four numbered sizes of Philips and Pozidriv, and even more for flat blades, that suit the differing gauges of screws (e.g. 4, 6, 8, 10 and 12). Miniature watchmaker sets of screwdrivers and special screwdrivers for knock-down furniture make the range even more extensive (see Fig. 2).

Materials used to produce wood screws

The materials most commonly used to produce wood screws are mild steel (cheap and strong), brass (non-rusting and looks good), aluminium (to use with aluminium windows to prevent electrolytic action), Monel, stainless steel and silicon bronze.

Figure 2. A variety of screw tightening methods

Coatings used on screws

The following coatings are used on screws: zincplated (prevents oxidisation (rust) and looks good), hot-dipped galvanising (for use with treated pine to prevent corrosion), brass-plated and coppered (anti-corrosion and looks good), antiqued (for an aged effect), black Japanned (black paint and anti-rust). These are the most usual coatings, but there are others.

How ordered/sold

To purchase screws, certain information is essential: head type, length, gauge, material, coating (if any) and the amount required. Screws are sold individually, in plastic packs or by the boxful.

Advantages over nails

Screws have a better grip than nails and are easily removable.

Hints for using screws

As a general rule, when choosing the length of a screw it should be approximately three times the thickness of the top piece of material.
Always ensure that a screwdriver fits correctly into the screw slot and is not worn (if a flat bladed one is worn it can be reground but the Philips and Pozidrive type must be replaced.
To avoid problems when driving screws into timber, always ensure that the screwdriver is vertical and that your hand and elbow are perfectly in line with it. Always push as you turn-whether tightening or loosening the screw (until it is really loose).
Rubbing a little wax or soap across threads will reduce friction when driving the screws.
When using several slotted screws, as in shelf supports or hinges, it is good practice to head the screws, which means ensuring that all the slots in the screw heads line up and follow the direction of the wood grain.
When mounting a frameless mirror (through holes drilled in the glass), special brass countersunk screws are used that have a small threaded hole in the top. It is important not to over tighten against the glass and then screw on small domed chrome caps to hide the screws.
When using brass screws, which tend to break easily, it is good practice to first use a steel screw of the same size. This creates the thread, which is then ready for the brass screw.

Nails

First known and used in Roman times, nails were forged from pure iron until the advent of the drawn wire nail following the invention of steel in the nineteenth century. Table 2 illustrates a selection of more common nails, their heads and uses.

Size

Nails are measured in millimetres based on their overall length and diameter.

Materials used to produce nails

Today, nails are manufactured from steel wire. In fact, a high percentage of the steel wire that is currently produced is used in the manufacture of nails. For external and marine applications, nails are also made from copper, silicon bronze and Monel metal.

Coatings used on nails

Hot-dipped galvanising (for use with treated pine to prevent corrosion), nickelled, brassed, blued and cadmium plated coatings are available for nails. These are all mainly used for their noncorrosive effect.

How ordered/sold

To purchase nails certain information is essential: head type, length, diameter (in millimetres), material, coating (if any) and the amount required. They are sold by weight normally, and are still available loose, in plastic packs or by the boxful. Nails for nail guns are sold in strips.

Advantages over screws

Nails are cheaper than screws and, in a nail gun, are very much faster to use.

Hints for use

See the section on hammers and mallets in for advice on using hammers.
See the section on butt joints for information of dovetail nailing, which leads to improved holding power.
When nailing two flat pieces of timber together, avoid nailing the nails all in line as this may split the wood. Stagger the nail positions by zigzagging them.
As a guide for choosing the correct length when nailing across the grain into the second piece of wood, use nails with a length that is approximately three times the thickness of the top piece. If going into the grain of the lower piece, there is less holding power; therefore, use a nail with a length that is approximately four times the thickness of the top piece.
Use the thinnest nail that will do the job as this reduces the chances of the wood splitting.
For using nail punches and putty see ??????.
For removing nails with pincers and claw hammers see ??????.
If you are using nails near the end of a board, for example when assembling a corner joint for a box, there is a possibility of splitting the wood up to the end grain. This can be avoided by blunting the tip of the nail so that it acts like a punch rather than a pointed wedge while it is going through the wood. To blunt the tip, turn the nail upside down on a solid metal part of a vice and lightly tap it with a Warrington hammer (don't bend it). Another method to avoid splitting the wood is to pre-drill holes slightly smaller than the nail's diameter, but this is time-consuming.

nuts

bolts

Knock-down fittings

Knock-down fittings are those that can be put together easily, by non-specialists, normally using only a screwdriver, a drill, a mallet/hammer, or other basic tools such as an allen key. They are designed to be temporary joints although many are used to permanently join together items such as cabinets and other pieces of furniture that are purchased in a flat pack.

These fittings have been developed to enable flat packing of furniture items made of solid wood and manufactured board. They are especially suitable for particleboard and MDF, which lack the grain strength of solid timber. Ikea is a well-known example of a manufacturer of flat pack furniture that is assembled by the customer.

The large array of knock-down fittings are classified in three ways: thread tightening, locking with a wedge action and locking with a cam action (see Table 1).

Source: Good Wood Joints by Albert Jackson & David Day.

Knockdown fittings

Table 1. Varieties of knockdown fittings

What is flat pack furniture?

Also known as ready-to-assemble furniture, it’s manufactured in flat parts and is self-assembled by the customer. Flat pack furniture is often constructed from manufactured boards such as particleboard and MDF. Flat pack furniture will have the separate components packed in carton boxes with instructions on how to assemble them on your own, along with simple tools, screws, and nuts.

Advantages and disadvantages of flat pack furniture

It is relatively cheap to produce and is therefore cheaper for the consumer to purchase. Flat pack furniture is usually made from manufactured boards and must be an uncomplicated, simple design so that the consumer can assemble it.
It "packs flat", so it is much more efficient to transport. This significantly reduces transportation costs, a benefit to the manufacturer and reduces the cost for the consumer. This also has an environmental benefit as less energy is required for transportation.
It uses materials more efficiently. Flat pack furniture is usually made from manufactured boards such as particleboard and MDF which is a more efficient way of using timber resources (see Manufactured boards, their manufacture, properties and use for more detail). Individual pieces are created via computerised manufacturing processes (CAM) using industrial CNC machines, these processes are carefully designed to minimise the amount of waste material produced.
Can be difficult to assemble. Sometimes it’s hard to assemble the items. Problematic instructions and leftover screws are the most common complaints customers seem to have, not to mention endless hours (and arguments!) spent trying to assemble furniture.
Low durability. Another disadvantage of flat-pack furniture is the damage due to its low sturdiness. Knock-down furniture is usually made from manufactured boards such as particleboard or MDF, which is not as durable as solid timber, especially if it has been dismantled and put together several times already.
Too simple design. Flat pack furniture is particularly suited for modern design styles. Simplicity of production and simplicity of construction are fundamental features of Flat pack furniture. Flat pack furniture tends to look the same and can be quite bland, limiting style and originality.

Hinges

Hinges have developed extensively over recent years. Timber products like MDF and particle board have caused a rethink on hinge design in order to produce hinges that have a better holding power. There are now concealed cabinet hinges with a variety of opening angles, self-closing hinges incorporating a catch system and quick release mechanisms. The more common hinges are illustrated, named and their use given in Table 6.4. However, because there is such a wide range, only the fitting of a standard butt hinge is described below. Materials for most hinges can be found in steel, brass, plastic and electro-plated zinc, brass, antiqued and specialist coatings.

There are many other types of hinges but their use is more specialised so they are not mentioned here. Concealed cabinet hinges require accurate positioning and are packaged with a template to drill in the correct position.

Fitting a butt hinge

Marking

First, mark the position of the hinge. This is generally in from the end of the door by one length of the hinge. If the door is framed, make the hinge line up with the inner edge of the rail. If the door is to be flush with the carcase, the position of the hinge is square across its edge. If the door is to be surface-mounted square, position the hinge across the back of the door.
Now, sit the hinge exactly on the mark and square across the other end of the hinge (there should be no gap between hinge and mark).

The centre of the hinge knuckle must be level with the outer surface of the door to allow it to open at least 180° (failure to do this will strain the door, hinge and screws) so set a marking gauge from the middle of the knuckle to the outer edge of the hinge and mark a line showing how far in to chisel out waste.

Fitting

Some people prefer to make a few shallow, angled saw cuts across the waste area for ease when chiselling (caution-it is easy to cut too deep).

With a chisel, groundside facing the waste, lightly tap with a mallet right on the marked waste lines (note-the long edge is running along the grain and might split if hit too hard, also there is a likelihood that you will be chiselling very close to the inner edge of the door so do not lever the chisel or the wood might break away). The angle of the waste that is cut out should gently slope from half knuckle depth up to just the thickness of the flap. Now gently remove the waste and pare smooth after.

Position the hinge, mark the centre of each hole and make small holes to take the countersunk screws. Screw only one screw in initially and ensure it travels square until it is flush in the hinge.
Now, offer the door up to the carcase and mark across (remember it might be inside, or on the edge, of the carcase depending on your door size-recessed or surface-mounted). Mark out the area to be chiselled by marking around the hinges (removed from the door), then cut and chisel out the waste. Attach both hinges to the carcase with one screw in each then gently attach the door and try it for fit. If all is well, fit the remaining screws; if it is misaligned, make fine adjustments and refit using different screw positions (so the hinge doesn't get pulled back to the original spot).

Figure 1. Equally recessed hinge on a flush mounted door

Figure 2. Offset hinge leaves an unbroken line around the carcase

Tee hinge - Used on doors and gates as they give good strength and support and are easy to attach as they are generally not recessed

Piano hinge - Comes in a range of lengths and mainly used on lids or desktops gives good support along the length of the hinge

Barrel hinge - simple to install. Just drill aligned holes of the appropriate diameter and fit. Suitable for small, lightweight applications such as jewellery box lids, fine furniture.

Flush hinge - As the name implies, designed to sit flush and only requires one recess to be cut for fine furniture applications. Generally not as strong as others but lightweight.

Rising hinge - are used in the dining room, drawing-room – or on other internal doors where there is carpet fitted. These hinges are designed so that when the door is opened, it raises high enough to clear the thickness of the carpet. These hinges may also be used outside the home wherever the door or gate lies below the level of rising ground.

Parliament Hinges - designed to allow the doors to swing 180 degrees, maximising the external space through the doorway. Suitable for patio, external doors and window shutters. Sizes come in standard length of 100mm and width ranging from 100mm to 150mm.

Concealed Hinge - also see Knockdown fittings. These hinges are used in modern kitchen and wardrobe manufacture and are designed to be fitted into MDF or particleboard panels

Butt hinge - Most simple basic and common one available. Suitable for most projects as they are easy to attach, simple yet strong.

handles

knobs

staples/staple guns

Drawer runners

011144074.pdf

Tabletop fitting (Table clips - from syllabus)

When a top is fitted to a table frame, you must asses the rate of expansion or contraction of the wood in order to avoid joining two or more pieces of wood that expand at different rates.

In timber, expansion along the grain is almost non-existent, yet tangentially or radially it can be from 2% to 9%. Therefore, joining a piece of wood along the grain to a piece across the grain may produce a movement difference of about 1 mm for every 100 mm of joined timber. Figure 1 illustrates what can happen if expansion is not allowed for. Allowing for expansion is not necessary if the table top is manufactured board, because expansion is very low and matches the under frame rails ( which always run along the grain right around and, therefore, have very low expansion also) Figure 2 demonstrates some methods of attaching tabletops to frames.

Figure 1. The result of not allowing for expansion-joint forced open

Figure 2a. Methods of securing table tops of solid timber, plywood and particle board to frame; note also various edge treatments

Figure 2b. Shrinkage plate (button) may be from wood or metal but must have the elongated hole placed along the direction of expansion/contraction

latches

catches

shelf hangers

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