This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
The method of cutting veneers, as conducted by the Grand Rapids Veneer Co., is thus described. In the first place the log is drawn up an inclined plane by means of tackle, and brought under a drag saw on a platform at the top, where it is cut to the length required in order to fit the cutting machine. On one side of this platform, which is outside the factory building, is a row of steam boxes, in one of which the log is placed, and allowed to remain about 12 hours, emerging in a very soft and pliable state. This is necessary to prevent chipping and breaking while going through the cutting process, and also to render it more easy to cut. It is lifted from this place by a powerful crane, and after the bark has been peeled off, placed upon the cutter. A veneer cutter resembles a gigantic turning lathe, with a knife ground to a razor-like edge running the whole length of the log to be cut. It is very massive, the knife being backed with an enormous iron beam, and the other portions are fixed in an equally solid manner; for the slightest tremor or yielding in any part would tear the veneer and render it useless. The machine used by this company weighs 10 tons. The chuck consists of a large iron shaft, which is hammered into place by a heavy swinging maul.
The log having been placed in position, the cutter is set in motion. The log revolves against the knife, and the veneer is pared off in a continuous sheet. So smoothly and easily does the machine work that it is almost impossible to conceive of the enormous power that is exerted. The feed is supplied by means of a revolving screw, which may be gauged to produce a veneer of any thickness from that of a sheet of tissue paper to § in.
Of course there is a limit to the diameter which the machine can cut; and after it has done its work, a piece 7 in. in diameter is left. In plain native woods this can be easily put to other uses; but in French walnut burls it is too valuable to be lost. In such cases, therefore, the knot is fastened to a stay log on whose centre it revolves, and thus very little, and that the least valuable part, of the costly material is wasted. The ash burls, which the company are now cutting, are brought in from the surrounding country, and they avoid the necessity of a stay log by having a sufficient part of the trunk on which the burl grew left to serve for this purpose. As the sheets of veneer come off the cutter, they are taken to a saw which divides them into the required widths, and are then put through the drying machine to remove the moisture with which the steam bath that they have received has saturated them. The subject of drying has been one of the most serious problems with which those in the veneer business have had to deal. A dryer is used by this company, who claim that it is both thorough and rapid in its operation.
It consists of 2 series of steam-heated rollers, enclosed in an iron box, between which the sheets of veneer pass as through a planer, emerging in a thoroughly dry state and pressed perfectly flat. The drying is still further expedited by a blast of hot air forced into the iron box referred to by a fan blower. After going through this process, the veneers are taken to the second floor, and such of them as are intended to be sold in this state are packed away, while the remainder is made into 3-ply panels to be used in the manufacture of bedsteads, for looking-glass backs, etc. These 3-ply panels are made by passing the veneers through a glue machine, and then placing them in a press. Great strength is secured in these panels by having the grain of the middle layer of veneer run at right angles with that of the 2 outer layers.
Generally speaking, straight-grained and moderately soft woods are sliced off a log by a weighted knife with a drawing cut, the log, or burl, being 10 ft. long, and the veneers varying from 1/8 in. to 1/40 in. in thickness, the width corresponding, of course, to the diameter of the log. A knife machine which gives a half rotary movement to a semi-cylindrical turned log, allowing a veneer to be cut following the log's diameter, produces wide veneers from logs of small diameters. But such woods as ebony and lignum vitas cannot be cut with a knife, while finely figured and consequently close-grained mahogany, and some rosewood, are difficult to cut. The saw, therefore, has its place. Such saws must be very thin, and so finely adjusted that hardly the slightest variation will occur in the thickness of the veneers turned out. While a nicely arranged circular saw will turn out boards varying 1/20 in., which would be imperceptible, such a lack of uniformity in thin sheets would prove a damaging imperfection. Before being cut, the veneer material must be carefully steamed, the same as in bending. A tight box 12 ft. long, and 4 ft. deep and wide is used, and exhaust steam is utilized.
An ordi-nary wood like black walnut, which has an open grain, will steam sufficiently in 6 hours, but the close-grained South American woods require 36 hours. Mahogany will steam sufficiently in 24 hours. Mahogany, tulip, and rosewood, being hard to cut, require more and careful steaming, and a knife in the best condition. The veneers wrinkle when laid together, but straighten out readily when glued properly to a body. Veneers will dry in the air in about 12 hours, but are not kiln dried, although the hitter method is used for lumber out of which veneers are to be made.
The softest woods should be chosen for veneering upon. Perhaps the best for the purpose are 12 ft. in length, of perfectly straight grain, and without a knot; of course no one ever veneers over a knot. Hard wood can be veneered - boxwood with ivory, for instance; but wood that will warp and twist, such as cross-grained mahogany, must be avoided. The veneer, and the wood on which it is to be laid, must both be carefully prepared, the former by taking out all marks of the saw on both sides with a fine toothing plane, the latter with a coarser toothing plane. If the veneer happens to be broken in doing this, it may be repaired at once with a bit of stiff paper glued upon it on the upper side. The veneer should be cut rather larger than the surface to be covered; if much twisted, it may be damped and placed under a board and weight over-night. This saves much trouble; but with veneers that are cheap it is not worth while taking much trouble about refractory pieces. When French walnut burr is buckled or cockled, as not unfrequently happens, it is treated on both sides with very thin hot size, and, when quite dry, placed between hot plates of zinc, or hot wooden cauls. This is done with the whole veneer, and it is cut afterwards.
The cutting is not easy, owing to the tendency of the veneer to split. It should be placed on a flat board, and marked to a size a little larger than necessary; the veneer is then cut lengthwise by a steel point or marker against a straight-edge, cuts across the grain being done with a fine dovetail saw. Very plain wood can be cut with a chisel or shoemakers' knife. Walnut burrs are best cut with 6cissors.