The Technique of FURNITURE MAKING

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 metric weights and measures will necessitate a complete overhaul of existing practices, and it has yet to be decided what conventional units will be adopted. At present bulk quantities of timber in continental countries are often measured in cubic metres (steres) but as a cubic metre contains 35.3150 cu. ft some smaller unit may eventually be adopted. In the meantime the procedures already mentioned are the same. The average of three widths over the face usually favours the buyer, and a measuring device incorporating sensitive fingers has been developed which will give extremely accurate readings. A similar device has been used for many years in the leather trade for measuring hides.

Metric conversions: inches to millimetres

Metrication

Some confusion still exists within the Timber Trade in the implementation of the metric system of weights and measures, and attempts to introduce intermediate units of measurement (centimetres, decimetres, etc.) have so far failed. Timber continues to be sold by the cubic foot (foot cube) as the cubic metre is too large an amount for most individual requirements, although metres and millimetres are increasingly being used for linear, cross section and surface measurements. Wood-working tools, brasswork, etc. are still made to imperial measure with metric equivalents, and this is likely to continue for the foreseeable future.

Metric conversions: imperial to metric units

Length

1 inch = 25.4 mm (millimetres) 1 foot = 0.3048 m (metres)

Area

1 square inch (1 in2) = 6.4516 cm2 (square centimetres)

1 square foot (1 ft2) = 0.092 903 04 m2 (square metres)

Volume

1 cubic inch (1 in3) = 16.387 064 cm3 (cubic centimetres)

1 cubic foot (1 ft3) = 0.028 32 m3 (cubic metres) ; 1 UK fluid ounce = 28.41 ml (millilitres)

1 UK fluid gallon = 4.545 961 (litres) (160 fl oz)

Mass

1 ounce (avoirdupois) = 28.350 g (grams)

1 pound (avoirdupois) = 0.45359237 kg

(kilograms)

Density

lbs per cu ft to kilograms per cu metre:

1 lb/cf = 16.018 kg/m3

Pressure

lbs force per sq in to kilograms per sq cm:

1 lbf/in2 = 0.070 31 kgf/cm2

Temperature

Degrees Fahrenheit to degrees Celsius (Centigrade):

5 (degrees F—32) .

—i— 9....................... = degrees Celsius

Degrees Celsius to degrees Fahrenheit:

—'—5-------- ' + 32 = degrees Fahrenheit

Conversion factors

To convert multiply by

inches into millimetres 25.4

millimetres into

inches 0.039 37

square inches into square centimetres 6.4516

square centimetres into square inches 0.155

Wood-scribe

This is a folding knife with hooked blade giving a gouge-like cut, and sometimes called a 'raze - knife'. It is used for marking the superficial footage on the ends of planks, and for scoring the weathered face of the wood to determine grain and colour.

2 Veneers

The term 'veneer' is unfortunate as it can mean to 'gloss over' or 'to cover up', but the practice of veneering dates from before the time of the Pharaohs, and is not, as some people still mistakenly imagine, a cheap method of glossing over poor workmanship and materials. Cogent reasons for the practice are fourfold:

(a) a more balanced construction is achieved, free from the inevitable splitting, checking,

warping and distortion of solid wood;

(b) the availability of rare and highly decorative timbers is vastly extended by using them in sheet

form;

(c) decorative effects, duplication of identical grain configurations to form matched panels and patterns are possible which would be extremely difficult with timber in solid form;

(d) certain rare and costly burrs, burls, curls and abnormal grain effects have very little structural strength, and would split, buckle or distort if used in any appreciable thickness.

The only disadvantages of veneered work, i. e. chipping and lifting of edges, fragility of top surfaces, etc., and lack of sparkle in the wood itself due to excessive glue penetration, have now been largely eliminated with the use of resin glues which form permanent bonds that do not—or should not—penetrate to the wood surface; and synthetic lacquers which provide extremely hard protective coverings which are proof against most risks in normal use.