The Technique of FURNITURE MAKING

Choosing wood

There is no consistency of quality in wood and every merchant or dealer can only offer the best of what is available in the particular species at any given time. First-hand inspection of the stock is always essential, therefore. Again, only active experience can give the knowledge of what constitutes good quality in any particular species. As an example, the writer would probably accept large rotten cores in rosewood logs, large knots in prime quality English walnut, very small pin knots in prime English oak, but no defects whatsoever in Honduras and African (grand bassam) mahoganies, sapelewood or Burmah teak.

In choosing wood the planks or boards should

be turned over and abnormal defects rejected or allowed for in the measurement. Top boards which are badly cast or showing considerable sap should not be included. Thicknesses up to 1 in (25 mm) should be reasonably free from splits except at the extreme ends, and if there are knots or shaky patches they should be ringed with chalk and allowed for in the final measurement. A certain degree of splitting in thicker planks must be expected, but is only permissible if usable wood is left on either side. Some degree of warp in wide boards is inevitable (but not in quartered stuff), but here again a centre-cut should yield reasonably flat surfaces on either side. Again, slight bowing in the length is allowable, but pronounced kinking, casting or cupping is not, although much depends on the nature of the wood, and a richly figured log might exhibit very considerable distortion. Heart and star shakes in the pith or crown plank are almost inevitable in logs from mature trees, but pronounced cup

rings

Beech

Sycamore

or ring shakes should be rejected out of hand as they have a habit of following up the tree for considerable distances, and may thus render the planks useless for all normal purposes. Seasoning defects should be looked for, particularly deep sticker-marks, extensive discoloration, sun checking, etc., although dry English oak may show large tarry patches which do not penetrate below the surface. If a mild working wood is required then the annual rings should be examined; they should be evenly spaced and as regular as possible and from eight to 16 rings per in (25 mm). Generally speaking, the wider the rings in hardwoods the stronger the wood, but the reverse applies to softwoods. Figures 22 & 23 show an example of beautifully grown yellow pine with tight, evenly spaced rings beside a comparable example of mild English oak. As the true colour of the wood and the extent of the sap is usually masked by dirt or weathering, most merchants will allow scoring the butt end with a knife, although they would object to its use across the face; it is therefore better to carry a small block-plane for testing. Thicknesses should be more but never less than the nominal size quoted, and a sharp eye should be kept for badly sawn or taper-cut planks which occasionally pass unnoticed. Imported square edge wood does not, as a rule, exhibit the same defects as waney/wane edge timber, as these have been rejected during conversion; more­over the plank and boards are usually graded before shipment. Points to look for are bowing in the length and inferior gradings slipped into the pile, otherwise the board can be accepted as it rises, choosing the most suitable widths and lengths. As the length of seasoning time is unknown the moisture content should be tested before use, and it is always better to buy square edge wood well in advance of requirement. Kiln-dried wood will be more expensive than air-dried, unless the latter has been in stick for several years. It is not wise to assume that kiln - dried wood will contain any less moisture as this depends entirely on how long it has been in storage since drying. On the whole, however, good kiln-dried wood, no matter where it has been stored, will tend to be less liable to subsequent distortion as the initial drying will have been carefully controlled.

Terms

The following terms are used in the timber trade, but although some are more applicable to softwood gradings they are also used in American hardwood gradings and are therefore included.

Terms denoting quality

Butt length Main trunk. Specifically lowest part of trunk next to stump.

Boule French term for superior timber or wood, but specifically imported logs sawn

through and through and reassembled in order of cutting.

Prime The best available in the particular species at any particular time. First quality.

Selects Selected wood.

Clean Free from knots.

Clear Free from visible defects.

C and S Common and Selects.

Mercantable Free from defects impairing strength, i. e. sound construction timber.

FAS Firsts and Seconds.

faq Fair Average Quality.

U/S Unsorted.

Av spec Average specification, i. e. dimensions according to the species.

Denoting withdrawal of certain dimensions from original specification.

As stacked without grading or selection.

Centre plank containing pith and heart shakes.

Wood converted so that the whole of the heart including pith and centre shakes is contained in one piece.

Crook Knee ) Short length of naturally curved wood.

Slabbing Outside slices of the log containing bark and sap.

Brashy Short-grained or old, dead or carroty wood.

Brittleheart Brashy heart caused by compression failures in fibres during growth.

Blackheart Abnormal black or dark brown discoloration in heartwood not necessarily

decayed as in blackhearted ash, etc.

Shipping dry Sufficiently dry to prevent deterioration (fungoid growths, mould, etc.) during

shipment only. (Average moisture content 25 per cent.)

Bone-dry Meaningless term suggesting thoroughly dry wood.

Terms denoting treatment

Converted timber Timber/lumber sawn from log.

t and t Sawn through and through/plain sawed. Waney/wane edge timber.

W/E Waney edge timber following the shape of the log.

S/E Square edge timber, i. e. waney edge timber trimmed up with edges parallel.

U/E Unedged boards.

1 W/E, 1 S/E One waney edge, one square edge from logs squared one side before sawing.

Quartered{ Radial cut timber following path of medullary rays.

Quarter sawn >

Rift sawn

Plain cut Tangentially cut flat sawed through the log (the middle planks will be quarter

Slash cut cut).

Flat cut )

Cleft Split or riven along the natural cleavage-lines following the medullary rays.

Surfaced Planed on faces but not to final thickness.

Thicknessed Planed to exact thickness.

Prepared Planed to final width and thickness.

par Planed all round, i. e. prepared.

pe Planed edge, or plain edge not tongued as in floor-boards.

t & g Tongued and grooved.

t g & b Tongued, grooved and beaded.

t g & v Tongued, grooved and vee-jointed.

Deeping Resawing through the thickness, i. e. parallel to the wide faces.

Flat Cutting Resawing through the width, i. e. parallel to the edges.

ad Air-dried

kd Kiln-dried.

For other terms refer to appropriate chapters.

dimension

Quarter of the girth taken as one side of the equivalent square in measuring wood in the round.

System used in timber measurement of round logs which allows about 27 per cent for waste in milling (bark and wane, etc.).

Allowance for bark.

Short round log. Short timber split or hewn. Log centre cut and squared or dressed.

Timber cut to specified dimension and left full to allow for subsequent treatment.

Square-edged boards of random widths.

Sawn timber over 2 in (50 mm) thick and of varying widths (British Standard 565:1963).

Sawn timber up to 2 in (50 mm) thick. (Many home-grown timber-merchants or lumber dealers prefer to regard Boards as up to 11/4 in (32 mm) thick and Planks as over 11/4 in (32 mm) thick).

Wood of small cross-section. Specifically square sawn softwood 1% in (48 mm) to 4 in (102 mm) thick and 4 in (102 mm) to 8 in (204 mm) wide.

Strip wood of small section. Specifically 3/16 in (5 mm) to 3/8 in (9.5 mm) thick and 1 in (25 mm) to 11/4 in (32 mm) wide.

Square sawn timber 2 in (50 mm) and under thick and 2 in (50 mm) to 51/2 in (140 mm) wide.

Square sawn timber 2 ft (0.60 m) and 2 ft 6 in (0.76 m) long by 11/2 in (38 mm) by 11/2 in (38 mm) and up.

Square edged dimensions not conforming to other standard terms.

Timber sawn to specified sizes.

Short lengths 3 ft (0.91 m) to 5 ft 9 in (1.75 m) long and widths 6 in (152 mm) and up.

Short narrows less than 6 in (152 mm) wide.

Cubic foot 12 in (304.8 mm) by 12 in (304.8 mm) by 12 in (304.8 mm), i. e. 0.02832 m3.

Square foot (0.09290 m2) superficial or face measure.

Board foot, board measure, denoting 1 sq. ft (0.09290 m2) (25 mm) thick.

Running foot (25 mm) length measurement in the particular width.

Average lengths.

All widths.

Nominal or sawn size before machining.

Converted timber/milled wood of less than specified dimension.

Sawn size before machining, i. e. planing.

Net measurement after machining.

Exact length/finished length.

The maximum permissible variation for a specified dimension in the sawn size.