COMPARATIVE PROPERTIES OF SOLID WOODS AND MANUFACTURED BOARDS Advantages of manufactured boards
1 Plywood and laminboards, etc. have no natural line of cleavage and cannot be split across the length or width, as the grain direction of each alternate layer is opposed …
DEFECTS IN PLYWOODS, ETC
Certain defects regularly occur during or after manufacture, and should be diligently searched for otherwise they may give endless trouble. Figure 26 gives the most common defects. Ripples or bumpiness …
FIBRE BOARDS
Fibre boards have been used extensively in the building industry for many years in various densities, but until recently the only application for furniture-making was the dense hardboard used for …
PARTICLE BOARDS (CHIPBOARDS)
These are composed of wood chips carefully graded, mixed with synthetic resin glue and either pressed or extruded into rigid, selfsupporting sheets of uniform thickness which are sanded down to …
Blackboards, laminboards, etc
In these the principle of construction is a series of wood core strips glued together side by side to form a slab, which is sandwiched between outer layers of veneer …
Stability
As wood is a hygroscopic material, shrinking and swelling under varying temperature/ humidity conditions, plywood, which is composed entirely of wood, must also shrink and swell, but the total movement …
Bending properties
Although plywood is normally used as a flat material, its natural resilience enables it to be bent to reasonably small radii of curvature without fracturing. The safe minimum of curvature …
Plywood dimensions
In all usual sizes the length of the face grains is given first, irrespective of the length of the sheet. Thus a plywood sheet quoted as 48 in (122 cm) …
Plywood grades
Grading rules differ according to the country of origin, and the following list is therefore a general indication only. A Face and back veneers practically free from all defects. A/B …
Grading and classification of plywood
Clear distinction must be drawn between the grading of ply, which is concerned only with the quality of the face veneers, and the classification into groups or types, which is …
Manufactured boards
These can be grouped within three broad classifications: Plywoods These are composed of layers or strips of solid wood glued together in simulation of solid wood, viz. plywood, laminboard, blockboard, …
MAN-MADE VENEERS
Reference should be made to a comparatively recent development which for lack of a better term can only be described as 'man-made veneers'. The process, first developed by John Wright …
Flat cutting or slicing
Originally carefully selected flitches of wood suitable for veneers were dogged down to a horizontal bed within the machine, and a heavy knife mounted on a rigid carriage slid backwards …
MANUFACTURE OF WOOD VENEERS
Before the introduction of power-driven circular saws all veneers were sawn by hand, usually 1/8 in (3 mm) and over in thickness, with deep saw kerfing which had to be …
Marking and measuring timber (metric measure)
Continental exporters cut to inch dimensions for the British and American markets and are content to do so for so long as the demand exists. However, the general adoption of …
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. …
Seasoned wood
The terms dry, bone dry, well seasoned are relatively meaningless without supporting evidence, for any wood which has been sticked one year for every inch (25 mm) of thickness may …
BUYING WOOD, AND TRADE TERMS Notes on buying wood
Buyers of waney/wane edge timber in small quantities direct from the saw-mill or timber - merchant or dealer must expect to pay considerably more per foot than buyers of complete …
PROPERTIES OF COMMON WOODS
The following list gives descriptions of some of the more widely known woods suitable for furniture-making. In each case, colour, texture, figure, working properties and behaviour can only be an …
STAINS IN WOOD
Stains can be caused by harmless fungi as distinct from wood-rotting fungi, soil conditions, frost factors, etc., chemical contamination, and natural oxidization or weathering. Stain identification Positive identification of any …
Giant wood-wasps
These only attack the living tree, and are, therefore, the foresters' concern. An occasional mature wasp of somewhat terrifying aspect. much bigger than a hornet and with a long egg …
Death-watch beetle (Xestobium rufovillosum) (21 :C)
This is a larger cousin of the furniture beetle, about 1/4 in (6.3 mm) to 1/3 in (8.5 mm) long and without the characteristic punctures on the wing-cases. The mature …
Common furniture beetle (Anobium punctatum) (21:A)
Commonly known as woodworm, this is the most serious pest, and commonly occurs in roof rafters, floors or general woodwork, including furniture. A few flight holes on the surface of …
Insect pests
21 Wood-boring beetles Most important of these are the lyctus, death - watch and furniture beetles; and of secondary importance, in that they attack only unseasoned, sickly or softwood timber, …
True dry rot (Lacrymans merulius)
This is an indoor type, and of all the wood - destroying fungi the most serious as it will attack dry seasoned timber if the conditions are suitable. Initially, the …
DISEASES AND PESTS
Wood which is deeply buried in the ground or completely submerged in water does not decay, as witness the highly prized black bog oak which has been buried for centuries …
Artificial defects
All woods shrink on drying, some pronouncedly so, thus creating internal strains and stresses. Normally, the natural elasticity of a healthy wood structure will distribute these stresses evenly, but if …
Natural defects
Knots These are in effect the basal stumps of incipient or cast-off branches in the living tree. Where the tree itself naturally prunes its branches owing to lack of light …
Fire resistance of wood
Although wood might appear to be one of the most inflammable of materials, some species, notably crab wood, jarrah, iroko, padouk and teak, are very resistant, and all woods of …
Durability
Hardness is no criterion of durability even though most, but not all, durable woods are essentially hard and dark in colour, due to the higher content of wood substance and …
Coloration
The natural colouring agents in wood are water soluble, and will tend to leach out if repeatedly soaked or exposed to weathering for long periods. Typical colour examples are logwood, …
Texture
Texture is concerned with the relative size and arrangement of the cells. Thus a wood with large open pores usually referred to as coarse grain is more correctly coarse textured; …
CHARACTERISTICS AND DEFECTS Grain, texture and figure
While the general term grain is normally used to cover many different characteristics of wood, e. g. straight grain, coarse grain, curly grain, raised grain, etc., strictly speaking it should …
Shrinkage factors
Shrinkage factors along the length can usually be ignored for they are only fractional, but both tangential and radial shrinkages can be considerable, according to the particular species. Unfortunately, the …
Shrinkage
A full understanding of the reasons for the shrinkage of wood, the probable extent of the movement and the direction it is likely to take (wood is not a homogeneous …
