The Technique of FURNITURE MAKING

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 and forwards over the table to give a shearing cut. In more modern machines, how­ever, the bed is vertical, moving upwards and downwards, again with a diagonal shearing action, against a fixed knife usually 1/2 in (12.5 mm) thick, 7 in (178 mm) wide and capable of cutting a 17 ft (5.18 m) length with every stroke. The knife is fed forwards by the thickness of the veneer being cut for each downward stroke of the bed, and is capable of very fine adjustment and accurate cutting of veneers from 1/250 in (0.1 mm) to 1/4 in (6 mm) or more in thickness.

Flat slicing of veneers gives a smoother, finer cut than rotary peeling, but even so there is always a tendency for the fibres to be plucked or torn, as in hand-planing across the grain. The best and most decorative results are obtained from true quartered flitches, where the direction of the cut is at right angles to the annual rings; whereas if the cut transverses the full width of the log it will go with the rings for half the width and against them for the other half. The effect can often be seen in sliced gaboon construction veneers, where one half of the width of the sheet is cleanly cut and the other half woolly and uneven.

The cutting of all veneers is highly specialized, for the logs must be steamed correctly, at exactly the right temperature for cutting (wet heat softens wood), and dogged down at the right angle, with the thickness and speed of cut determined by long experience only, and an instinctive appreciation of how the wood is likely to behave. Face veneers, as distinct from construction veneers, are usually cut either 0.88 mm, 0.83 mm or 0.71 mm thick (28. 30 or 35 to the inch), the last familiarly known as "seven mil' (0.71 mm), with the thicker veneers a better compromise against excessive glue penetration and torn grain. Continental veneer-cutters often cut 40, 50 or even 60 sheets to the inch (25 mm) with little regard for plucked grain and tissue-thin patches. Such veneers are much cheaper, but should not be used in good work.

Reference has already been made to 'Semi­rotary' cutting, in which suitably shaped flitches are mounted off centre in the lathe so that the cut is half-slice, half-rotary peeling action. This cutting method is sometimes employed for special grain effects, notably in Rio rosewood, etc.. but has been largely abandoned owing to the enormous torque created by the off-centre flitch, and consequent heavy wear on the lathe.

Veneer thicknesses

TYPES OF VENEER Page 47

While rotary peeling is usually reserved for ply­wood manufacture, constructional veneers for laminated work are normally sliced in 1, 1.5, 2.5, 3 and 4 mm thicknesses from beech, obeche, gaboon, limba and similar woods. Backing quality veneers used as balancers on the underside of groundworks (see Veneering, marquetry and inlay, Chapter 32) are usually peeled or sliced to V32 in (0.7 mm) or thinner out of sapele, straight-grain mahogany, makore (cherry mahogany), etc. Both constructional and backing veneers are normally sold in bulk quantities, but can be obtained in small amounts from retail dealers if specially ordered. They are considerably cheaper than the usual run of face veneers, and one suspects that backing veneers are often used for face-work in cheap furniture. There can be no objection to this for the veneers are cleanly cut from prime logs and are usually lacking only in decorative effect, although occasional bundles will be the equivalent of a good African mahogany or sapelewood face veneer. Saw-cut veneers are now virtually unobtainable except as odd lots, but kingwood is still saw-cut. Face or decorative veneers are usually sold by the cutters in part or complete logs, composed of several bundles according to the number of flitches the log has yielded. This 'buying as they rise' and taking the good with the bad—for practically all trees have some defect or other—is obviously much cheaper than choosing selected bundles from any one stock, and most veneer-cutters in a large way of business will not permit 'breaking the log'. For the small user there are many retail dealers who buy in bulk and sell a few leaves at a time, although the price asked must necessarily be several times that of a bulk purchase.

In choosing veneers it is always a wise precaution to examine each bundle very thoroughly, for beautiful veneers are inter­national currency. They may pass through several hands and are easily damaged. Reputable firms do not hide defective or damaged leaves in the middle of the bundle as a matter of policy, but transposition can occur. Curls, burrs/burls and feathers, etc. are numbered and should be in strict order as cut, for although there may be no apparent difference between adjacent sheets, the small variations build up, and the difference between the first and last sheet of, say, a 30-leaf bundle can be very considerable. Such bundles are rarely, if ever, split, and must be bought as a whole. Highly decorative veneers should never be ordered from one sample leaf only; inspection of the whole stock is essential. To cite just one example—a single Rio rosewood log may yield bundles ranging from a very plain light tan to rich inky black figuring.

Veneer varieties

It would be impossible to list all the varieties available at any one time, for every wood species is capable of yielding veneers, and every tree in the species is an individual with different grain structure, coloration and abnormalities. Add to this different methods of cutting, rotary peeling, semi-rotary peeling, quartered slicing, crown cut (tangential cut), etc., and the permu­tations are endless. There are, for example, over 300 different species of oak commercially available; the mahoganies form a vast family, while walnuts include English, French, Italian, Ancona (Italian), Circassian, Caucasian (Persian), Australian and American. Names also change according to the locality or at the whim of the dealer, with common agba elevated to tola branca, white tola, etc., to give only one example. Add to this abnormal grain effects— roe, bird's eye, blister, dapple, mottle, quilted, stripy, swirled, burr/burl, crotch, stump, pollard, fiddleback, curl, fan, feather and flame—and the endless variety ensures that wood as a means of decoration is irreplaceable so long as people remain individuals and hanker after individual things. A full description of the matching, jointing, preparation and laying of all types of veneer is given in Chapter 32.