Manufacturing individual components as part of a project

Legs

Rails

Drawers

High-quality drawers are constructed with a lapped dovetail at the front and a common dovetail at the back (but other joints can be appropriate).

Front joint

For light use, a tongue and trench joint or a rebate may be used. With the simple rebate, cut to three-quarters depth. The side can be strengthened by two or three thin panel pins nailed into the end grain of the front piece from the side. This puts the pins into a condition of shearing if the front were to be pulled off.

If a false front is to be fitted then the inner front and sides can be joined with butt joints because adding the false front virtually changes the joint to a rebate (see Fig. 1). False fronts are fitted when a thicker front is needed for shaping (i.e. a gentle curve), or if it is necessary for the front to extend to a wider width all around and locate against the front of the carcase rather than be flush with it. If you are using solid timber, always try to select the best grain figure for the front where it will be noticed and appreciated.

Back joint

For the back of the drawer, a joint that is simple yet strong is the through housing. The main load on a drawer back occurs when the drawer is opened quickly and any loose weights inside it slide to the back of the drawer. The housing cannot come apart as it is captive in a groove. Another advantage of this joint, because it has to be set forward of the corner by about 30 mm, is that you can open the drawer to view all of its contents yet still have the drawer supported by the last 30 mm or so (a little internal space is lost). See Figure 1.

The base

Unless a drawer is very shallow, it is bad practice to just nail a base onto a drawer because the whole drawer rubs on the shelf below and the front edge of the base will be seen. The usual (easiest) method for attaching the base is to cut a groove around all the pieces before they are joined. The back, however, has the lower section under the groove completely removed. This is so that when the four sides are glued up the base can be made, fitted and slid in from the back with a couple of fine countersunk brass wood screws inserted from underneath up into the back to stop it coming loose and to support it. Slide-in bases like this do not have to be glued and this makes them renewable should damage occur.

Another method of fitting a base is to nail and glue a slip around the inside of the drawer. A slip is a strip of wood with a slot cut into it to allow the base to slide in on it (see Fig. 1). Materials for bases include MDF, veneered MDF (one

side), hardboard, embossed hardboard and, best of all, plywood because it can be grain matched and has uniform strength in both directions due to cross banding in its construction. Solid wood drawer bases are mostly not used anymore because of a lack of long-term seasoning, and because of the time and expense involved in constructing them.

Drawer stops

Drawers should not hit the back of the carcase. If stops (small wooden blocks) are placed near the back, the position of the drawer front will alter with expansion/contraction of the drawer length (EMC change). However, if thin stops are placed near the front, this is less likely to be so noticeable. The recognised method is to make two small pieces of plywood, about 40 mm long x 20 mm wide, and glue them each side, so that the lower inside of the drawer front just touches them at the closed position (5 or 10 mm before touching the back of the carcase).

Drawer design and construction has been unavoidably altered by manufactured board products. This is basically because manufactured board products are made of woodchips or fibres, which have no continuous grain. Therefore, new joints were developed because ones like dovetails could not be used as they would break easily Design changes have also been necessary because of flat packing since construction must be straightforward for the person (who may have no woodworking ability) assembling the product. Even some plastic drawers are made in a continuous strip that just has to be folded into shape and tapped (no glue necessary) into a prejointed front (the base being the part keeping everything square).

Figure 1. Joints commonly used in drawer construction

Making Dovetailed Drawers.pdf

Illustrated guide to drawers.pdf

Doors

Tops

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

Figure 3. Breadboard end for a table top

Breadboard ends - 4 methods.pdf

Keeping tabletops flat.pdf

Panels

Google Sites

Report abuse