Choosing the right types of wood when working with timber is important. Before you can make anything successfully, you must have the right kind of wood for the purpose. There are, also, "choice cuts" in lumber, as the butcher says of meat, and judicious selection of the stock often makes all the difference between a good job and a poor one; so let us examine a log and follow it through the sawmill.
You have, of course, seen the rings, or circular lines, on the ends of pieces of wood (Fig. 9). These are called the annual rings, and each ring marks a new layer of wood added to the tree, for, as perhaps you may have learned, the trees we use for wood-working grow by adding new layers of wood on the- outside. Examine the ends of pieces of wood of various kinds. In some pieces these rings will be very plain. In others they will be quite indistinct.
Notice that the wood nearest the bark, known as the sap-wood, usually looks different from the inner wood, which is called the heart (Fig. 9).
In some trees you will see rays, or lines, radiating from the centre, and known as the medullary rays (Figs. 9 and 10), because they spring from the pith (Latin medulla).
So called because in the common trees of temperate climes one layer is added each year.
Sometimes these lines are too fine to be noticed.
Fig. 11The way the log is sawed is important, though you might naturally think that the only thing is to saw it any way that will give pieces of the required size and shape.
It begins to dry and shrink as soon as the tree has been cut down. The sap-wood shrinks more than the heart because it contains more water, and faster because, being on the outside, it is more exposed. The log shrinks most in the line of the annual rings, that is, around the tree. It shrinks much less in the line of the medullary rays, that is, across the tree. Shrinkage lengthways is too slight to be considered. (Fig. 11).
The result of all this unequal shrinking in different types of wood is that the log tends to split, or crack open, at the circumference (Fig. 12); the cracks running in toward the centre, in the line of the medullary rays.
If the log is halved or quartered, so that the inner parts are exposed, the drying goes on more uniformly throughout, the cracking is not so bad, and the parts of the log will shrink somewhat as shown in Figs. 13 and 14.
The beams, joists, planks, or boards cut from a log have the same tendency to shrink unevenly that is found in the log itself. This causes them to be irregular in shape and to curl or warp more or less, according to the part of the log from which they are taken. A piece cut from the centre of a log will thus hold its shape better than if cut from one side.
Although the shrinkage lengthways is not usually noticeable as affecting the length of a board, it shows slightly by its effect in causing the pieces to spring, or become bowed lengthwise, as you will see in many boards which have been left free to spring while seasoning.
When a log is sawed into boards or planks (Fig. 16) the middle board shrinks but little in width and in thickness at the centre, but becomes thinner towards the edges. It does not curl, because it is cut through the centre of the log and has no more tendency to curl one way than the other.
The outside board shrinks least in thickness and most in width, and all, except the middle one, shrink differently on one side from the other. They become convex toward the pith, or heart, and concave toward the outside. Different types of wood shrink and warp to different degrees. You can learn something about these matters by examining the stock in any lumberyard.
Now to come to the practical application of our brief study of the log and the sawing process of different types of wood: if you merely wish to get the most that you can from a log in the form of boards or plank, have the pieces sliced off in the simple way just shown (Fig. 17). This is the usual way of sawing for ordinary purposes. Boarding for the outside of a house, for instance, cut in this way answers every purpose. By this process the central boards will be good and the outer ones inferior, as just shown (Fig. 16), but for common work all can generally be used.
If you want the highly patterned grain seen in types of wood like oak, ash, chestnut, etc., you can get it by sawing the log as just shown in Fig. 17. The grain will be most marked in the outer boards (Fig. 18), because the annual rings are cut more obliquely in them than in the boards at or near the centre. These boards (Fig. 17) will tend to change their shape, as just shown (Fig. 19), but if they are to be firmly fastened in some way, or confined (as in a panel), handsome grain effects can be obtained.
In addition to the curling, the outer boards will be poorer because they contain a greater proportion of sapwood, which is usually inferior to the heart-wood.
By this is not meant the figure or flashes shown by the medullary rays, or "silver grain," seen in quartered oak and some other woods, but the figure of the grain without the medullary rays, as seen in types of wood like plain oak, etc.
If you wish the beautiful figure formed when the medullary rays show on the surface of the board, as in "quartered" oak, the log should be cut in the direction of the radii, that is, along the lines of the medullary rays (Fig. 20). The more exactly the side of a board is cut on the radial line the more richly the figure of the medullary rays will be shown, as in Fig. 21. This method of sawing is more expensive than the first way, of course, as it requires more labour and wastes more of the wood. The wide board shown in Fig. 21 and either of those in Fig. 22 are examples.
If you wish boards that will shrink the least in width and remain as true as possible, then the log should be sawed on the radial lines as just shown, so that all the boards will be from the middle of the log. Wood shrinks but little in the direction of the radii, as just shown, and middle boards will be alike on both sides as regards heart and sap-wood, etc., and, therefore, have the least tendency to change of shape. The middle board by the method of Fig. 17 will be a good board in these respects.
Split or rift stock is stronger than sawed. If you wish a piece especially tough and durable, as for an axe handle or a stout pin, it should be split out rather than sawed, unless the wood is very straight-grained, because the splitting is sure to be in the line of the fibres, thus avoiding "cross-grain," which cannot well be entirely prevented in sawing.
If the grain is straight, there may be no practical difference in the result between sawing and splitting, as in the so-called rift flooring, which is really sawed, but with crooked-grained pieces the difference is marked in such cases as the block shown in Fig. 27, from which four pins can be sawed, while but one can be split out. That one will be straight-grained, however, and stronger than the sawed ones, which will be cross-grained.
Do not believe the statements so common in books that it "takes lumber " some definite time, as one year or two years, "to season." It all depends on the types of wood, its shape and size, the condition of the atmosphere, and various circumstances. For some rough work (a pig-pen, for instance) there is no advantage in seasoning at all, because the stock can just as well dry after the work is done as before.
For many kinds of common work one or two years is sufficient for some types of wood and sizes of wood; for a nicer grade of work two or three years is none too much, while for very nice indoor work four years or more is not too long for the stock to season. There is very little danger of its being kept too long. It never will get perfectly dry. Whether it is dry enough or not depends on what you want to use the wood for.
It is no exaggeration to say that in factories where cheap furniture and other common articles are made nowadays, a standing tree is felled on Monday, the log rolled into one end of the factory, and before Saturday night the finished articles made from it, all varnished and complete, are sent out from the other end of the shop - and some articles are turned out even quicker.
In the natural process of air-drying the moisture gradually and slowly works out to the surface and evaporates, until the wood is seasoned, though never absolutely dry, and the stock is firmer, more elastic, and less affected by heat and cold, moisture and dryness, than if kiln-dried.
The latter process tends to dry the outside and ends of the lumber too fast for the inside. It certainly lessens the elasticity of the wood and weakens it. Making it so unnaturally dry (as if baked), as is often done, only makes it more susceptible to the atmosphere when taken from the kiln, and, unless it is at once protected from the air in some way, it will reabsorb moisture until it gets into a more natural condition; but that will not fully restore the loss of elasticity . The deterioration in the quality of the wood can be plainly seen by any woodworker, and is often a subject of remark in regard to oak.
The kiln-drying of different types of wood "takes the life out of the wood," as workmen express it, but just why this is so is not easy to explain, for the structure and properties of wood are very complex. Lumber left for years to season naturally, "stands," as the expression is, better than if kiln-dried - a fact which is, I think, generally conceded by woodworkers who have had experience with both kinds.
The gain by kiln-drying, in time and money, is, therefore, more or less offset by impairment of the quality of the wood, so if you can find stock that you know has been seasoning for years by the natural process, buy it by all means for your nice work, even if you have to pay more, regardless of what the dealers in kiln-dried stock or the makers of articles for sale may tell you about the advantages of kiln-dried wood.
On the other hand, if a dealer brags that he can make green wood "dry as a bone" in two or three days, go elsewhere to buy your stock, for wood dried in a few days is not the kind to use for good work. You will probably have to use kiln-dried stock for most, or, perhaps, all of your work, but get it from a slow-drying kiln and keep it for further seasoning as long as you can.
Even if wood has been well seasoned, it is best, before putting it into nice work, to cut it up and dress it approximately to shape and leave it in a dry place for some time for a final seasoning, particularly in the case of thick stock. Do this with kiln-dried stock fresh from the dry-house. Let it have a little time to get into harmony with the atmosphere. Whenever wood has been exposed to damp air, as in a wet shed or cellar, let it stand in the warm shop a while before using it for nice work.
One test is to rap the different types of wood boards sharply with a hammer. A green board and a dry one of the same kind will " rap " differently, - that is, will have a different vibration and give out a different sound. Of course this cannot be described, but you can judge quite well in this way. It is one of the many things you can learn only by experience. You can ascertain much about the character and condition of various types of wood and lumber by sawing or planing or whittling a piece. This is a good test for dryness, toughness, and elasticity (which you can tell about by breaking the shavings).
Weather-dried timber is usually somewhat darkened from exposure, but kiln-drying lightens the colour of some woods.
Stock with a bright lustrous appearance and of dark hue is generally superior to that of a lighter colour and duller appearance, but such characteristics depend much upon the kind of wood. Green wood is tougher than seasoned wood, but the latter is more elastic. To subject seasoned wood to moisture and heat brings it back, to a certain extent, to its original condition, and renders it for the time being tougher, hence the process of bending wood by the application of steam or hot water.
For plain work avoid "cross-grained" stock, as well as that having knots (which are sometimes "tight " and sometimes "loose"), as it is harder to work and to smooth, is not as strong, and does not hold its shape as well, as a rule. Sometimes it is desirable, however, on account of the beautiful figure of the grain shown in many crooked-grained pieces, as in mahogany for furniture. Bear in mind that when especial strength is required rift stock is best. Reject wood which smells musty, or has rusty-looking spots, which are signs of decay, or of the attack of fungi, which may spread and under favourable conditions attack other pieces which are sound.
Reject crooked stock. The worst form is winding or twisting. Of course no one would take such an extreme case as Fig. 29, unless for some very rough work, but even a very slight winding may make much trouble in your nice work. So look particularly for this defect, which you can often detect at once by the eye, but if your eye is not well trained use winding-sticks. Warped or curled stock, with the surface rounded or hollowed (Fig. 19), is also bad, but you will need no instructions to detect this defect by the eye or any straight stick.
When boards are rounding on one side and hollowing on the other, it is due either to the way the log was sawed, as we have seen, or to one side having been more exposed and so having dried faster and shrunk faster than the other, causing that side to be concave, while the other became convex. Stock is sometimes crooked lengthways, - either a simple bending in a curve or at an angle, or wavy (Fig. 30), or both, - often due to careless "sticking" (Fig. 28) while the wood was green. Sighting lengthways will of course show these defects.
Reject stock badly checked at the ends, or cracked. There is apt to be more or less of this in most lumber. In seasoning, the pieces dry faster on the outside than in the middle, which causes checks or cracks, usually worse at the ends of the pieces, where the drying takes place most rapidly. The ends of valuable boards and planks are sometimes painted or cleated, which in a measure prevents this result. Occasionally, when the cleat is removed a crack will suddenly extend and even split the board.
Do not take a cracked or partly split board, thinking that you can use the sound end from the point where the crack appears to stop. Possibly you can, but oftentimes and in some kinds of wood it is impossible to tell before the stock is cut where the cracks end. In mahogany, for example, they sometimes are found to extend, or develop, several feet beyond where they appear to stop. Sometimes you can buy such types of wood with these defects at a discounted price. Unless you are sure, however, that there is enough sound, clear wood outside of the cracks or knots, and unless the discount is pretty large, it will usually be better to buy clear, sound stock for nice work, as the waste is very apt to offset the saving, not to speak of the extra time and labour it takes to work up such material.
Reject sapwood as far as possible, because it is usually inferior to the heartwood.
"The sapwood is, as a rule, darker in the whitewood class than the heartwood, whether seasoned or unseasoned, but is paler in colour in most hardwood trees which have had time to season. In some of the white, or softer woods, when fresh cut, the difference is scarcely perceptible; but exposure to the air quickly gives to the outer layers a greenish tinge, due to a species of mould fungi which attack them." - Laslett and Ward.
When buying different types of wood, do not take boards just as they happen to come from the pile. Select them yourself. Most good-natured dealers will let you do this if you do not expect them to unstack a whole pile just for one or two boards. It is better to do this for nice work even if a slight charge should be made for the privilege. When you come to pick out boards you will see the application of what has been said about the ways of cutting the log, and you can tell by the annual rings at the ends of the boards, by the sapwood (when visible), the grain, etc., from what part of the log the pieces were sawed.
Use good, clear stock for everything but rough work. Of course in rough or temporary work you can save expense by using wood from packing-cases, boxes, old fence-rails, or anything that will serve the purpose, but as a rule avoid trying to make nice, new things of wood taken from old work or boxes. The quality of the wood used for boxes nowadays is apt to be poor and hard to work. The wood taken from old cabinet-work is, however, often better than you are likely to buy, but you need to be very cautious about working over old material, for the dirt which has been ground into it is apt to dull your tools, and, moreover, the presence of concealed nails, etc. (which it is sometimes almost impossible to detect), will often injure your tools so much as to more than offset what you save in expense
Do not buy thick stock with the idea of sawing it into thinner pieces (unless necessary). Of course it can be sawed into thinner or smaller pieces, but you cannot always be sure that these will be as true as the original stock. Suddenly exposing the middle of a piece of wood to the air in this way sometimes plays queer pranks with the shape of the pieces. If you want to use boards for good work buy those which have seasoned as boards, instead of splitting up thicker lumber; and always try to treat both sides of a board alike so far as you can.
Bear this in mind: If you take an inch board to the mill to be planed down to three eighths of an inch, for instance, have it planed equally, as nearly as may be, from both sides. Ignorant hands often simply smooth off, or "surface," one side, and then plane the board down on the other side, when it will sometimes warp badly at once and be useless, perhaps, for the purpose intended.
If you carefully pile and "stick" the stock you have bought (Fig. 28), it will tend to keep the pieces straight and true. Never lay good boards down flat directly upon one another unless they are thoroughly seasoned. It is the best of all ways, however, to keep a pile of thoroughly seasoned stock, but not the way to season it. The top board will warp. Never lay a single board of nice stock flat on its side. Keep short pieces of nice stock standing on end where they will be equally exposed on both sides to heat and cold, moisture and dryness.
The best way to learn about types of wood is from the wood itself. It is a good idea to make a collection of specimens of as many kinds as you can. You will be surprised to see how varied, interesting, and handsome a collection of these various types of wood you can make at little or no expense. It then becomes a good reference tool and identification board for the different types of wood.
The types of wood which you are likely to use are commonly known as either hard or soft, the former class from trees with broad leaves, as the oak, the latter from the coniferous or needle-leaved trees, as the white pine. This distinction between hard and soft wood you may find somewhat puzzling at first, for the common whitewood of the hardwood class you will find softer and easier to work than hard pine of the softwood class, but the distinction is based on botanical reasons. The hard woods are usually more durable as well as stronger than the soft.
Lumber consists, according to Webster, of "timber sawed or split for use, as beams, joists, boards, planks, staves, hoops, and the like."
Lumber may be either undressed or dressed, that is, rough (as it comes from the saw) or planed. It is usually sawed in regular thicknesses, and for stock which is in steady demand, such as joists, floor timbers, etc., in regular widths, as 2 " x 4," 4"x6 ", etc. It is commonly sold in lengths varying from 10 feet to 20 feet.
Twelve feet is a common length for boards. Planing (by machine) rough or undressed boards on both sides will usually reduce the thickness of an inch board to about seven eighths of an inch.
Other thicknesses will of course be reduced correspondingly. Bear this in mind. The terms 1 " board, 2 " plank, etc., apply, as a rule, to the stock in the rough state as it comes from the saw. When you buy planed or dressed lumber it will be thinner - that is, the "inch board " that you wish to get for a shelf will not be one inch thick (unless you get it unplaned), but seven eighths of an inch.
You must make allowance for this when you figure on dressed lumber. If for example the board must be one inch thick when planed, you will have to get a thin plank and have it planed down, or pull over the pile until you find a board which happens to be sawed as thick as one inch and one eighth.
You can sometimes find boards planed one inch thick, but as a rule you will find the thickness seven eighths of an inch. A similar statement will apply to the various thicknesses of planks also. The sawing is often very irregular, however, and frequently some boards or planks will run thick enough in sawing to give the required thickness when planed, so it is well to look for such when you need pieces a little thicker than planed stock usually runs.
For such work as you are likely to do you will chiefly need boards, planks, and joists. Other forms will be referred to farther on.
The word timber is applied in a general way to the log and to the material itself, and to the standing trees. It is also applied more specifically to the larger squared pieces, or " dimension "stock, such as sills, beams, etc.
These are one inch thick or less.
Matched-boards, or "sheathing," have a groove on one edge and a corresponding tongue on the other (Fig. 31.) Any number of boards can thus be joined to make a wide surface. The edges of these boards were formerly tongued and grooved by hand with "matching-planes," but now this is done by machine, usually with some form of bead or moulding at one edge (and sometimes in the middle) to render the joint less noticeable.
These are thick boards, - more than one inch in thickness. Both planks and boards can be of any width or length, the distinction being merely in thickness.
These are the same as narrow planks, but of some fixed width, as 2 " by 3 ", which is the same as a 3 " strip sawed from the edge of a 2 " plank.
Most of the types of wood you will require is sold by the square foot, at so much an M (1000 feet), or so much a foot. The square foot has an area of 144 square inches and is one inch thick, or contains 144 cubic inches, regardless of the shape or size of the piece. That is, Figs. 32, 33, and 34 each equal one square foot by board measure.
Thus a board 12' long, 12" wide, and 1" thick, contains 12 feet, board measure. A board 12' long, 6" wide, and 1" thick, contains 6 feet. A plank 12' long, 12' wide, and 2" thick, contains 24 feet. A plank 12' long, 6" wide, and 2" thick, contains 12 feet, or the same as the board first mentioned. You can bear in mind that in case of boards 12' long the contents in feet is indicated by the width in inches, as you will see from the examples just given. A board 12' long and 7" wide contains 7 square feet. So all you have to do to measure 12' stock is to find the width in inches.
If the board tapers in width, measure at the middle. The same is true of planks, only the width in inches must be multiplied by the thickness of the plank. A plank 12'long, 7" wide, and 3' thick, contains 21 square feet. Of course this principle can be quickly applied to pieces whose length is any convenient multiple or fraction of twelve. Thus a board 18' long, 8' wide, and 1" thick, contains 1 1/2 times as many square feet as one 12' long, or 12 feet. A plank 9' long, 6" wide, and 2" thick, contains 3/4 as many square feet as if 12' long, or 9 square feet.
Boards less than one inch thick are usually sold by the square foot of surface, regardless of thickness - the price varying according to the thickness, except in cases where an inch board is planed down, when, of course, inch thickness is charged for. There is no distinction made in measuring between a rough board 1" thick and a planed board 7/8", as, of course, they represent the same amount of lumber. The cost by the foot of the planed board is greater because of the expense of planing. In cities, and sometimes in the larger towns, you can find thin boards (1/2", 3/8", 1/4", 3/16", 1/8" thick) already planed, and even scraped, for nice work.
Some of the rarer and less commonly used types of wood are often sold by weight, such as ebony, leopard wood, tulip wood, etc. Pieces turned out in quantities for special uses, as strips, mouldings, etc., are often sold by the "running foot," meaning simply the length, the price varying according to the amount of lumber and labour required. Certain regular sizes and shapes of lumber are sold by the piece. Shingles, clapboards, laths, and the like, are sold in bunches or bundles.