KING’S SERIES IN WOODWORK AND CARPENTRY

ELEMENTS OF WOODWORK

BY

CHARLES A. KING

DIRECTOR OF MANUAL TRAINING

EASTERN HIGH SCHOOL, BAY CITY, MICHIGAN

NEW YORK ·:· CINCINNATI ·:· CHICAGO

AMERICAN BOOK COMPANY

KING’S SERIES IN WOODWORK AND CARPENTRY

ELEMENTS OF WOODWORK

ELEMENTS OF CONSTRUCTION

CONSTRUCTIVE CARPENTRY

INSIDE FINISHING

HANDBOOK FOR TEACHERS

Copyright, 1911, by

CHARLES A. KING.

Entered at Stationers’ Hall, London.

W. P. I.

PREFACE TO THE SERIES

This series consists of five volumes, four of which are intended as textbooks for pupils in manual-training, industrial, trade, technical, or normal schools. The fifth book of the series, the “Handbook in Woodwork and Carpentry,” is for the use of teachers and of normal students who expect to teach the subjects treated in the other four volumes.

Of the pupils’ volumes, the first two, “Elements of Woodwork” and “Elements of Construction,” are adapted to the needs of students in manual-training schools, or in any institution in which elementary woodwork is taught, whether as purely educational handwork, or as preparatory to a high, or trade, school course in carpentry or vocational training.

The volumes “Constructive Carpentry” and “Inside Finishing” are planned with special reference to the students of technical, industrial, or trade schools, who have passed through the work of the first two volumes, or their equivalent. The subjects treated are those which will be of greatest value to both the prospective and the finished workman.

For the many teachers who are obliged to follow a required course, but who are allowed to introduce supplementary or optional models under certain conditions, and for others who have more liberty and are able to make such changes as they see fit, this series will be found perfectly adaptable, regardless of the grades taught. To accomplish this, the material has been arranged by topics, which may be used by the teacher irrespective of the sequence, as each topic has to the greatest extent possible been treated independently.

The author is indebted to Dr. George A. Hubbell, Ph.D., now President of the Lincoln Memorial University, for encouragement and advice in preparing for and planning the series, and to George R. Swain, Principal of the Eastern High School of Bay City, Michigan, for valuable aid in revising the manuscript.

Acknowledgment is due various educational and trade periodicals, and the publications of the United States Departments of Education and of Forestry, for the helpful suggestions that the author has gleaned from their pages.

CHARLES A. KING.

Bay City, Michigan.

PREFACE TO ELEMENTS OF WOODWORK

In preparing this book, it has been the author’s purpose to present, in as complete and concise form as possible, the knowledge which every wood-worker should possess regarding the care and use of his tools and the material upon which he employs them.

Whether an amateur, apprentice, or skilled workman, whether a carpenter, boat builder, pattern maker, or wood carver, the elementary knowledge of the construction of tools, of sharpening them, and of their adjustment and manipulation is practically the same. The structure of wood, and the necessity of applying its peculiarities of grain and texture to the advantage of the work in hand, also is the same upon all branches of woodwork.

While innumerable tools and cutting devices have been invented to enable the wood-worker to accomplish special results economically both as to time and material, a study of them will prove that they all operate upon a few simple principles, a knowledge of which is not difficult to acquire, though skill and judgment in the application of the tools can be attained only by continuous and properly directed practice.

It would be both impossible and unnecessary in a book of this sort to describe these various devices, though in a schoolroom it is a great advantage to have as many of them as practicable, not for their use only, but that the students may become familiar with their purposes and the applications of the fundamental principles upon which each is based.

The actual use of tools may be considered the A B C of woodwork, as it bears the same relation to the finished product of the workman as the alphabet bears to literature, the space between the mere mechanical facility in the use of either tools or alphabet, being the result of the judgment, skill, and individuality of either the workman or the author.

Thus, if a student acquires the facility to use the tools described in this volume, he will have little difficulty in using other and more complex tools; and when he has mastered the principles of construction involved in the exercises explained in the following book of this series, the “Elements of Construction,” and the correct use of the tools involved in making these, together with their applications and combinations, he has acquired the fundamental knowledge of all construction in wood.

CHARLES A. KING.

Bay City, Michigan.

TABLE OF CONTENTS

LIST OF ILLUSTRATIONS

ELEMENTS OF WOODWORK

CHAPTER I

Growth of Wood

1. Kinds of trees used for lumber.—(A.) The classification of trees here considered is based upon the method by which the trunk, or stem, of a tree is formed. The term exogenous is applied to outside growers, around which a layer of wood grows each year, and from which is cut the lumber of commerce. As the wood-worker is interested mainly in trees which grow by this method, we will do no more than mention the endogenous, or inside-growing, trees or plants of the nature of palm trees, cornstalks, etc., in which the woody fiber is formed upon the inside of the stem.

(B.) The new wood formed each year upon exogenous trees is known as the annual layer, or ring; the separate layers being more prominent in open-grained woods, such as oak, ash, and chestnut, than in close-grained woods, such as maple, cherry, poplar, and birch. It is the difference in the character and structure of these layers which makes some woods hard and others soft, some with open and others with close grain, and which also, with the coloring matter peculiar to each kind of wood, causes its individuality and adaptability to certain uses. (The color and odor of wood are caused by chemical combinations, and are not part of the substance of the wood.)

Fig. 1.—Section of Yellow Pine.

a, soft, cellular grain; b, hard, compact
grain.

Each of these annual layers is composed of two parts, the formation being shown in Fig. 1, in which the grain of yellow pine is depicted. The soft, cellular, or open, grain, a, is formed as the sap moves upward in the spring, and the hard, compact grain, b, is formed later in the year. In soft woods the open grain predominates, while in hard woods the compact grain is more in evidence.

The age of a tree may be determined by counting these annual rings upon the stump, though a drouth during the growing season may have at some time so affected its growth as to make some layers indistinct, rendering it impossible to be absolutely sure of the count. In a young tree the annual layers are thicker than when the tree becomes more mature.

(C.) The different kinds of timber which the carpenter uses are cut from deciduous, or broad-leaf, trees, and from coniferous, or needle-leaf, trees. This classification of trees is based upon the difference in the forms of their leaves, the former kind furnishing the ash, oak, walnut, beech, birch, and other woods that are hard to work, as well as poplar or white wood, linn or bass wood, and others which are called hard woods, not in the sense that they are hard to work, but because their method of growth is the same.

The coniferous or evergreen trees furnish the cedars, pines, hemlocks, spruces, firs, redwood, tamarack, cypress, and a few other woods of the same nature. These woods have a resin which is always present, no matter how old or dry the wood may be, which explains their superior weather-resisting qualities.

2. The formation of wood.—(A.) In the spring the sap begins to flow upward, mainly through the open cells of the cambium (the new growth in the stem, by which the diameter of the tree is increased), and to some extent through the sapwood. As it comes in contact with the air by means of the leaves and the green shoots of the tree, (B.) it gives off water and oxygen, and absorbs carbonic acid gas from the air, (C.) which is formed into starch, sugar, oil, etc.; this in turn becomes part of the sapwood, and forms the compact part of the annual ring, completing the layer for that year.

(D.) The wood is formed by a deposit of matter from the sap, which gradually thickens the cell walls until the cells are filled, when that layer becomes a part of the heartwood, or that part of the tree which is inclosed within the annual layers of sapwood.

(E.) Both the fibers and the cells of the sapwood are filled with water or sap, which may be removed by seasoning, but the sapwood of most trees used for building purposes is not as good lumber as the heartwood, as it is always susceptible to moisture. The exceptions to this will be mentioned elsewhere.

(F.) In all unseasoned lumber from 20 to 60 per cent of its weight is moisture, which must be evaporated before the lumber has its highest commercial value. This may be done by weather drying or by artificial means, the lumber being treated in a specially constructed kiln.

3. Tissues.—(A.) A tree trunk is composed of four different tissues, viz.:

1. The pith (Fig. 2, a), a cellular tissue: this is worthless and its presence in lumber is considered a defect.

2. The wood, which includes the heartwood (b), the sapwood (c), and the medullary rays (g). From this part of the tree the commercially valuable lumber is taken.

3. The cambium (d), which is a thin layer between the sapwood (c) and the bast (e).

4. The bark, which includes both the bast (e) and the outer bark (f). The bark of most trees is worthless, but that of chestnut, oak, hemlock, and other trees which are rich in tannic acid is used in large quantities by tanneries.

(B.) The heartwood (b), or duramen, of most trees is the part generally used by carpenters upon the best work. It is firm, compact, and of the color and qualities characteristic of the wood.

(C.) The sapwood (c), or alburnum, is generally light-colored, and in most building woods its presence is considered a defect, though not in hickory, ash, maple, or yellow pine, and a few other woods; in fact, in these woods it is often preferred to the heartwood for many kinds of work on account of its color. The alburnum is filled with the active elements of the sap, which are deposited as the sap passes through the trees, and in time becomes part of the duramen, or heartwood. The time required for sapwood to attain maturity ranges from thirty to one hundred years, according to its kind and age.

Fig. 2.—Section of Oak Tree Trunk.

a, pith; b, heartwood, or duramen; c, sapwood, or alburnum; d, cambium; e, bast, or inner bark; f, outer bark, or corky layer; g, medullary rays, or silver grain; po, plain oak; qo, quartered oak.

(D.) Outside of the sapwood (Fig. 2, c) is the cambium (d), which furnishes the substance upon which the life of the tree depends. Here, nourished by the richest sap, new cells are formed, which become either sapwood or a part of the bast. (E.) At (e) is shown the bast or inner bark, which is composed of a woody fiber combined with a tissue of cells. This is elastic, which allows it to expand as the wood grows beneath it. Outside of the bast is the bark (f), or outer covering, which is of a corky nature, and protects the delicate vital parts of the tree.

4. The medullary rays.—Every tree has medullary rays (Fig. 2, g), usually spoken of by wood-workers as the “silver streak,” or “silver grain.” These rays connect the center of the tree with the outside, and are more prominent in such woods as oak, beech, and sycamore than in other woods. It is to take advantage of the beauty which these medullary rays impart that so much quarter-sawed lumber is used, though lumber sawed in this way is preferred for other reasons, which will be discussed later.

In many woods these rays are so small as to be invisible to the naked eye, as in pine, for instance, which has fifteen thousand to the square inch. Aside from adding much to the beauty of the lumber, they also give strength; if lumber is dried out too rapidly by artificial heat, it is apt to check, or crack, upon the line of the medullary rays.

Fig. 3.—Defects in Lumber.

a, wind shakes or cup shakes; b, heart shakes; c, star shakes; d, branch broken off, showing the method by which the annual layers gradually cover broken branches; e, hard knot.

5. The grain in trees.—In open or exposed situations trees usually grow more or less gnarled or crooked, which tends to improve the grain. The strength of lumber cut from trees grown as described is impaired, however, as the wood is more cross-grained than that from trees which grow in the heart of a forest, with practically the same conditions on all sides. As forest trees are continually reaching up for the sunlight, they grow taller and straighter, which makes it possible for straighter-grained lumber to be cut from them, and as the branches are at the top, where they receive the sunlight and air, there are few cross-grained places.

When the annual rings are large, the grain is said to be coarse, and if the rings are fine, the term fine-grained is used to describe it. When the direction of the fibers is nearly parallel with the sides and the edges of the board, it is said to be straight-grained; when the lumber is taken from a crooked tree, it is said to be cross-grained, as the grain follows the shape of the log, while the board is sawed straight. Cross-grained lumber is the handsomer; in this the fibers, being at different angles with the surface of the board, form a variety of figures, which add much to the beauty of the wood.

6. Defects found in lumber.—(A.) Some of the most common defects found in lumber are wind shakes, or cup shakes (Fig. 3, a), which are cracks following the line of the porous part of the annual rings. These are caused by the action of severe winds. (B.) Heart shakes (Fig. 3, b) are cracks radiating from the center of the tree, and may be found in any kind of wood, as they are the result of deficient nutrition, or loss of vitality. (C.) Star shakes (Fig. 3, c) are caused by the shrinkage of the tree upon the outside, which is the result of a long dry spell of intense cold, or of the deficient action of the sap. Star shakes differ from heart shakes in being larger upon the outside of the tree; the heart shakes are larger at the center.

Shakes of all kinds are common defects and sometimes are so numerous as to make the log worthless.

(D.) Discolorations are caused by decay which has at some time gained a foothold, but which the tree was sufficiently vigorous to overcome; or they may be due to imperfect or insufficient nutrition, which generally results in the entire tree being affected instead of small places upon the tree.

(E.) Timber grown in a damp, marshy locality is generally of a poorer quality than that grown upon higher ground, as more water is taken up by the roots than can be well assimilated, which prevents the formation of healthy compact wood. Some woods are adapted to such soil, the poplar or whitewood, willow, basswood, buckeye, and cypress being denizens of moist or swampy places.

Trees growing where they are exposed to winds from one direction are apt to assume a spiral growth, which renders the timber almost worthless, as it is weak, and twists badly in drying.

(F.) Trees which have lumps appearing like growths upon them are usually unhealthy. These lumps, or tumors, may be caused by defective nutrition, checks, or shakes, or by the depredations of animals or insects.

(G.) Clefts, or splits, in a tree may be caused by extreme cold, heat, or drouth. They may extend into the tree several inches, and while the blemish will always remain, showing a discoloration or other defect, nature often repairs it so that the strength of the timber is but slightly affected. If these clefts are not healed, rain may find lodgment there, and the sap be so affected that the adjacent wood will be destroyed, and this in time will destroy the tree.

(H.) Eggs of certain insects are also deposited in these clefts, the larvæ of which bore into the wood and destroy it. (I.) If it were not for the birds and other natural enemies of these insects, they would increase so rapidly that the lumber supply would be seriously affected, and, as it is, there are very few trees which are not injured to some extent by wood borers. The United States Bureau of Entomology estimates that the damage to trees by these pests amounts to at least $100,000,000 annually.

(K.) Sometimes (as at d, Fig. 3) branches die or are broken off; this gives the elements access to the heart of the tree and usually causes a permanent injury, as the birds and other denizens of the forest frequently dig out the rotten wood as soon as the weather has had time to do its work, thus giving further opportunity for decay to continue its destructive action. If this does not happen, the wood will grow over the break after several years and leave a loose knot in the heart of the tree, which will be a decided blemish when the log is made into lumber. The sketch shows the endeavor of nature to repair the defect, as the annual rings will eventually close over the break.

The hard knot at e, Fig. 3, is not a serious defect, unless the wood is to be used for finish or where great strength is required.

7. When to cut lumber.—Trees which are intended for the use of wood-workers should not be felled while the sap is in motion. If cut at any other time than midsummer or in winter, the active sap is apt to sour and to cause decay. Owing to the scarcity of lumber, or from avarice, this precaution often is ignored, and trees are felled at any time of year, regardless of their age; in such cases, much of the lumber lacks the essential qualities of its kind.

When a tree shows signs of dying at the top, it should be cut down, as the quality of the lumber it contains will deteriorate rapidly.

Suggestive Exercises

1. What is meant by exogenous trees? In what kinds of wood are the annual layers most prominent? Describe the formation of annual layers. What causes the difference in the degrees of hardness of wood? In the color and odor of wood? How may the age of a tree be determined? Are the broadest annual layers found in young or in old trees? From what class of trees does soft wood come? Hard wood?

2. Describe the motion of sap. What forms the sapwood? With what are the cells of the sapwood filled? Compare sapwood and heartwood.

3. Describe the four different tissues in a tree. Describe the inner bark.

4. What are the medullary rays? In what woods are they most prominent? How do they affect the strength of timber?

5. What is the nature of trees which grow in exposed situations? Where are the straightest trees found? Why does the location of a tree affect the grain? What is meant by coarse, fine, straight, and cross-grained lumber?

6. What causes wind shakes? Heart shakes? Star shakes? How may they be distinguished from each other? What causes discolorations? What is the usual character of timber grown upon marshy ground? What woods are adapted to low ground? What sometimes causes spiral growth? What do lumps and excrescences upon a tree generally signify? What causes clefts in trees? What are the results of clefts? Does nature perfectly repair the cleft? What is the usual result of a branch being broken off?

7. What is the per cent of moisture in green wood? Should very young trees be cut? Why? How may the top of a tree show when it should be felled? At what time of year should trees be cut?

CHAPTER II

Lumbering and Varieties of Wood

8. The manufacture of lumber.—(A.) There are two distinct processes in the preparation of lumber for commercial purposes, logging and sawing; the former includes all the steps from felling the tree to the delivery of the logs at the sawmill; there the logs are sawed into boards, planks, and timbers of certain dimensions, which are piled and exposed to the sun and air for a sufficient time to allow a large part of the water in them to evaporate, when the lumber is said to be “weather dried,” and ready for shipment to the consumer.

Fig. 4.—Felling a Tree.

(B.) If a lumber concern desires to begin operations in one of the great forest areas, a “land-looker” or “timber-cruiser” is sent to spy out the land, and to report upon the probable yield of timber within certain areas, and the conditions which would aid or retard the work of getting out the logs. If the report is favorable, the standing timber may be purchased by “stumpage,” which means that a certain price will be paid for each thousand feet of lumber cut, or the land may be purchased outright, though in the early history of lumbering cases have been known where these little formalities were omitted.

Fig. 5.—Cutting Small Branches from
Felled Spruce.

Camps are located at convenient points throughout the boundary, roads are made through the woods, and foundations, or “skidways,” built at right angles to them, to receive the logs as they are hauled down the “travoy” roads, which are narrow trails cut through the woods at frequent distances for this purpose.

(C.) The above preparations completed, the work of felling the trees is begun (Fig. 4); this part of the work requires nice skill and judgment, as it is necessary that the tree should fall so that it will cause the least damage to itself and to surrounding trees. After the tree is down, the branches are cut close to the trunk (Fig. 5) and carried to one side so that they will not be in the way of the horses. The trunk is then sawed into logs, twelve, fourteen, sixteen, or eighteen feet in length, as the imperfections and the length of the tree trunk may allow. Longer or shorter logs are rarely cut except for special purposes.

(D.) One end of the log is placed upon a drag, or is gripped by a pair of tongs, and hauled to the nearest travoy road and skidway, where it is piled (Fig. 6). (E.) From the skidway the logs are loaded upon trucks, cars, or sledges (Fig. 7), and carried to the cable (Fig. 8), which is a method of hauling logs used in some parts of the country, or to the railroad (Fig. 9), or floated down a river (Fig. 10). If either of these latter methods of transportation is employed, the logs are generally piled upon another skidway until there is enough for a train load, or until the conditions upon the river are favorable for them to be floated to the mill.

Fig. 6.—Skidway of Spruce Logs.

Fig. 7.—Load of White Pine Logs.

Fig. 8.—Hauling Logs by Steel Cable.

Fig. 9.—Loading Logs from Shedway to Train.

Fig. 10.—Boom of Logs.

Fig. 11.—Log Jam.

(F.) Figure 11 illustrates a jam of logs, which is generally the most dangerous obstacle the lumberman has to face. A jam usually depends upon one key log, which, if loosened, will allow the jam to break instantly. The work of loosening the key log is frequently done by one or two men, who must be men of spring steel nerves and muscles, and possessed of the highest possible skill and activity, or they cannot hope to break a large jam and escape with their lives.

Fig. 12.—Sawmill in the Big Tree District.

(G.) The mill illustrated by Fig. 12 is one which receives its logs by both rail and river. In this case the logs which come in by rail are rolled into the river, as they can be more easily placed upon the chain feed of the mill. In winter, a small pond of water is heated, in which the logs are soaked before they are taken into the mill; this draws the frost out of them, and allows them to be worked much more easily.

(H.) There are different types of sawmills, in which the logs are worked into commercial shapes. The small enterprises use portable mills, which are moved into the woods and located upon a tract of land, remaining until all the desirable timber in the vicinity has been sawed, and then moved to another locality and the process repeated.

Large operations are conducted upon a different plan; mills of a permanent type are erected as near the forest as practicable, roads are built, tracks laid, and the logs brought from the woods by one of the methods previously illustrated; or, where it is feasible, flumes are built, and the logs floated in these to the mill. In erecting a mill of this sort, a location is selected upon a waterway if possible, as the logs may be floated more cheaply than by any other method of transportation, though some of the heavier woods will not float, and have to be handled on land. (I.) The immersion of logs in water also improves the quality of the lumber, as the action of the water upon the sap prevents to some degree the tendency to decay, and also facilitates the seasoning of the manufactured product. If the log is left in the water until it becomes water-logged, it will sink, and while it is not injured for many purposes, the wood loses some of the strength which it is supposed to have. In many localities, the salvage of sunken logs has become an industry.

(J.) In modern large lumbering operations, the timber to be cut is selected by trained foresters, thus insuring a permanent supply, and in the near future all extensive lumbering operations will, beyond doubt, be conducted upon a scientific basis, as it is apparent that unless lumbering is carried on differently than it has been in the past, the supply for the future will be entirely inadequate for the demand.

(K.) In the smaller sawmills, the logs are usually sawed into lumber of various dimensions by a circular saw (Fig. 13); but in the larger mills, the band saw generally is used. Figure 14 illustrates a double cut band sawmill, in which it will be seen that the saw makes a cut each time the log is carried either way.

Fig. 13.—Circular Saw.

9. To saw lumber of irregular dimensions.—(A.) Besides sawing dimension timber, joists, scantlings, boards, and planks of different thicknesses are sawed, as follows: 1”, 1¼”, 1½”, 2”, 2½”, 3”, 3½”, 4”; and thicker, if desired.

(B.) If lumber is cut again from its original dimensions, it is said to be resawed. When boards or planks of the above dimensions are dressed on both sides, they will be about ⅛” thinner; thus, a board sawed 1” thick will, when seasoned and dressed, be but ⅞”, and a 2” plank will be but 1⅞” or 1¾”, though still classed by their sawed dimensions.

Thicker lumber than that above-mentioned usually comes under the head of dimension timber, which is not used to the extent that it was formerly, as steel and concrete are replacing it upon heavy work.

Fig. 14.—Double Cut Band Saw.

If ½” boards are wanted, 1¼” or “five quarter” lumber is usually resawed to furnish it, and after resawing, is planed upon each side to the desired thickness. Boards for box stock and other special purposes are sometimes sawed as thin as ¼”.

Fig. 15.—Plain, Slash, or Bastard Sawing.

Fig. 16.—Four Methods of Quartering.

(C.) The method of cutting a log illustrated by Fig. 15 is known as plain, slash, or bastard sawing, and is the cheapest way to cut logs, both as to time and waste. The log is first squared to secure a bed upon which it may lie while being sawed, which also makes it unnecessary to run each board by the edging saw to straighten the edges. The slabs at a are sawed into boards as the log is squared, and the bark, or “live edges,” sawed off afterward. These make an inferior grade of boards, as they are nearly all sap, but they are well worth saving, if large logs are being cut.

In sawing dimension timber, or “bill stuff,” good judgment is necessary to cut a log so that the greatest amount of marketable lumber can be made from it. This is done by cutting various sizes from a log, if it will not cut all of one size without too much waste.

(D.) In cutting woods which have prominent medullary rays or silver grain, the log is sawed by one of the methods shown in Fig. 16, the object being to bring the rays as nearly parallel to the surface of the board as possible, thus giving the broad silver, or quarter, grain which is so highly prized.

The best results are obtained from sections a, b; this method also gives the most waste. In plain sawed lumber, the boards from the middle of the log will have the quarter grain; these are usually culled and sold as quarter-sawed.

Neither of these methods results in economy of time or material, as about 25 per cent of each is used in excess of that required in plain sawing; hence, quarter-sawed lumber is more expensive than the plain, or bastard, sawed.

(E.) Quarter-sawed lumber (Fig. 16) is preferred not only on account of its handsomer grain, but because it holds its shape better than lumber sawed in any other way, as the annual layers are approximately square with the surface of the board. As the board shrinks in the direction parallel with the annual layers, and very little from the center to the outside of the tree, it is obvious that there is much less shrinking and warping in quarter-sawed lumber than in that which is sawed plain.

The best grades of flooring are quarter-sawed, and stand usage without the surface splintering much better than does the common plain sawed material. Quarter-sawed lumber is known also as “rift-sawed,” “vertical grain,” and “comb grained.”

10. The grading of lumber.—Custom varies somewhat in different localities as to the grading of lumber, but there are generally four grades, which are often subgraded into qualities suitable for various uses.

“Number 1” lumber should be practically perfect, though in large dimensions, small and unimportant blemishes may be allowed. These blemishes in a board are usually restricted to not more than one inch of sap, a small sound knot, or small discoloration, and but one blemish to a board is allowed.

“Number 2” lumber is generally allowed two sound knots, an inch of sap, and one other blemish.

“Common boards” are allowed three or four sound knots, but two thirds of one side must be clear stock.

“Culls,” the lowest grade, are used only upon the cheapest work. One half of the board must be usable.

In many cases the boards are graded by the width of clear stock which can be taken out. There are tables published by the different associations of lumber manufacturers which give the gradings under which their lumber has been measured and shipped, but as these vary from time to time no permanent list can be given.

The principal reason why there can be no permanent grading of lumber is that the forests from which the finest timber can be cut in marketable quantities are being destroyed faster than they can be replaced by nature. In anticipation of this condition, the Division of Forestry of the Department of Agriculture is actively engaged in organizing government forest preserves, in educating the people, and in promoting legislation aimed at the husbanding of our forests. When we consider the abundance of high grade lumber a few years ago, and the fabulous prices which the same grades now bring, it is evident that this movement should have begun during the days of our grandfathers, instead of waiting until nearly all the best lumber in the great forests east of the Mississippi had been cut, and inestimable damage wrought by forest fires.

11. The testing of lumber.—(A.) Dry, sound stock, if struck with the knuckles or with a hammer, will give a clear ringing response, while a wet or decaying piece will give a dull response to the blow.

(B.) Every kind of lumber has its peculiar odor, by which, as well as by the grain, the student should learn to distinguish the woods in common use. This may be more easily done before the wood has been thoroughly seasoned. Wood in general has a sweet and pleasing odor; if a sour or musty smell is perceptible, it indicates that decay is present.

(C.) If there is much variation in the color of timber, or black and blue spots, the stick is probably diseased.

(D.) Decay is a disease, which may be prevented by dryness or ventilation, and frequently may be cured by soaking the wood in water for several days, or by steaming. The disease of decay is cured also by chemical preservatives being forced into lumber by pressure; this at the same time prevents insects from boring into the tree.

Alternate wetting and drying will produce rot, but most lumber, if permanently submerged or if kept perfectly dry, will last almost indefinitely. Dry rot spreads to adjoining timbers, and even to those which have no connection with the one originally infected.

12. Surveying or estimating lumber.—(A.) It is the custom to consider any board less than one inch in thickness as an inch board, and anything over one inch is measured as so many inches and fractions of an inch. For instance, a board ¾” thick is surveyed as a full inch, while one which is sawed 1½” in thickness is estimated by obtaining its surface measure, and increasing it by one half. Thus, a plank 12’ long, 8” wide, and 1½” thick would have twelve feet board measure in it.

In some localities there is a sliding scale of prices which varies with each quarter inch in thickness of resawed lumber, but this is not universal.

(B.) In surveying joists or scantling, it is customary to obtain the fraction of a foot, board measure, for each lineal foot. Thus, a piece of 2 × 4 (inches understood) has two thirds of a foot for each foot in length; a 2 × 6 has one foot, and a piece of 2 × 8 has one and one third feet of lumber for each foot in length of lumber measured. If a joist is 2 × 12, doubling its length gives the number of square feet, board measure, that the joist contains.

(C.) In measuring a common board, the widest parallel piece which can be cut from it is the width of the board being measured; therefore the board should be surveyed at the narrowest place. In measuring more expensive lumber, it is customary to average the width of the board.

(D.) In estimating all kinds of lumber in common use, the lumber scale shown in Fig. 17 is used. It is made of thin, cleft hickory, about three feet long, with one end large enough for a suitable handle; on the other end is a metal head, which is held against the edge of the board while the scale is being read.

The length of the board is marked near the handle, and at the end of the socket of the metal head, as at a.

In using this scale, the hooked end, or head, is held against the edge of the board, as at b; the eye follows along the same line of figures upon which the length of the board is found, reading those figures nearest the width of the board. Thus, a scale laid upon a board 16’ long would, without further measuring or calculating, show that the board contains 17’ board measure. If the board were 12’ long, it would contain 13’; and if 14’ long, by reading the middle line of figures, the board would be seen to contain 15’.

In using this scale, it is customary to read to the nearest figure, and when there is no difference, to alternate between the lower and the higher figures upon different boards. Thus, a board 12’ long and 8¾” or 9¼” wide would be read as having 9’ board measure in it. Two boards 8½” wide, of the same length as the above, would be measured as having 8’ and 9’, respectively, in their surfaces. In short, the fractions of a foot are not considered in surveying the lumber in common use.

Fig. 17.—Lumber Scale.

13. Qualities of wood.—(A.) Certain kinds of wood are adapted for some purposes better than are others; the wood-worker, therefore, should be familiar with the qualities which conditions demand, and the kinds of woods which have these qualities.

Lumber for framing should be strong and durable; it should be cut from trees which grow to a size that will allow large dimensions to be cut from them.

For outside finish, the material should be wood which will stand the weather, can be easily worked, and will hold its shape well.

Timbers that are to be buried must possess the quality of durability, and should be of sufficient strength to resist the strain which will be put upon them.

Flooring should wear well, hold its shape, and be of good appearance. In providing lumber for inside finish, care should be used that it has good grain and color, is not too soft, and that it will hold its shape well. Almost any wood may be used as far as strength is concerned, but lumber which shrinks and warps badly is unfit for finishing.

Shingles should be of wood which will resist decay, and which has the least tendency to warp and split.

Boards which are to be used for siding should hold paint well, and be as free as possible from the tendency to warp, split, and twist when exposed to the weather.

(B.) All material used in framing a building should be weather-dried in good drying weather for at least thirty days for each inch in thickness, and that used for inside and outside finish and floors should be thoroughly kiln-dried, and kept in a dry place until ready for use. These conditions are not always obtainable, but if the best results are desired, they should be followed as closely as possible.

The woods hereafter described comprise the principal varieties used by the wood-workers of the United States.

(C.) Ash (deciduous, or broad-leaved) is an open-grained, light-colored wood, in which the porous portions of the annual rings are quite prominent, thus making it somewhat coarse-grained.

It grows in the Northern states, and is a wood of medium weight and hardness. It is tough and elastic, the young growth being much used in the manufacture of wagons, machinery frames, and for similar purposes, as it is not expensive, quite easily worked, and very strong. It has a tendency to decay, and is often badly infested with insects; therefore it is not suitable for building construction or for contact with soil.

Ash grows in forests with other broad-leaved trees, and is plentiful in many localities. There are two kinds of this wood recognized in commerce: the white, which is light-colored, and the black, which is of a brownish tinge, though there is little difference in the grain of the two. Sap is not considered a defect, but is regarded as the best part of the tree for some purposes. The wood grown in the Northern states is generally tougher than that grown farther south.

The wood from the older and larger trees is not so tough and hard as that from the younger growth, and is much used for cabinet work and for interior finish. It should be filled with a paste-filler, after which it may be brought to a fine polish. The wood holds its shape well and is useful for the purposes mentioned.

(D.) Apple (dec.) is not used for construction, as the proper dimensions cannot be secured, and as it is very stubborn to work. It is one of the best woods known to resist splitting, and is much used for chisel and saw handles.

(E.) Basswood, or linden (dec.), is a soft, porous wood, which shrinks considerably in drying. It is used for the backing of veneer work, for drawer bottoms of the common grades of furniture, for case backs, and similar purposes, and is also much used in the manufacture of spools and other small articles which are made in large quantities. In building construction, basswood is used for ceilings, and for other work where strength is not needed, though for use in such places it should be thoroughly seasoned, or the joints will open.

If steamed, basswood may be bent to almost any form. Steaming also cures to a great extent the tendency of this wood to shrink and swell.

(F.) Beech (dec.) is adapted for use in places where the ability to resist a heavy strain or hard wear is necessary, as in plane stocks, tool handles, and parts of machinery. In building work, it is used to some extent for flooring and for inside finishing. It is used also for furniture, though the difficulty of working it makes it more expensive than other equally desirable woods.

If exposed to alternations of dryness and dampness, it decays rapidly; if submerged, it gives fair satisfaction.

Beech trees are common through the Ohio and Mississippi valleys, and are found to some extent in all of the states between the Great Lakes and the Atlantic seaboard.

(G.) Birch (dec.) is one of our most useful hard woods. It is found in abundance in the broad-leaved forests of the Eastern states and Canada. There are two varieties recognized in commerce, the red and the white birch. The former is used considerably for inside finish and for furniture. It takes a stain well, and may be made to imitate cherry or mahogany so exactly as to deceive any one but an expert. When finished in its own natural color, it is a satisfactory wood for the above uses, but as it ages, it turns to a muddy brown; as it is a stubborn wood to work, it is not popular.

Fig. 18.—Beech and Sugar Maple Forest.

Canoe, or paper, birch is softer than the red variety, and is used to some extent by paper pulp makers, and for the manufacture of spools, dowels, and a large variety of small articles.

(H.) Butternut or white walnut (dec.) has a good grain and color; it is quite soft, though not so easily worked as are some harder woods, for it has a tendency to string while being dressed to a fine surface. It does not absorb moisture readily, and holds its shape under trying conditions.

Butternut does not split easily, takes a fine polish, and is used considerably for furniture and for interior finish.

(I.) Cedar (coniferous, or needle-leaved) is of two varieties, the red and the white. The former is used considerably for cooperage and veneers, lead pencils, and for lining moth-proof drawers and chests, as its strong odor and bitter taste protects it from the ravages of insects. The supply of red cedar is becoming limited, and it is now too expensive for common use, though our forefathers used it for shingles. The unwise and avaricious cutting of this valuable timber and of others, notably white and Georgia pine, has destroyed what would have been a supply for all time, if the cutting had been properly controlled.

White cedar is much more plentiful, and a much inferior wood; it is used for shingles, water tanks, boat building, and in the manufacture of barrels and cigar boxes. It is a very durable wood, and shrinks but little in drying. It is well adapted for burying, though not strong enough to resist a very heavy strain. It grows faster than the red cedar, and makes a larger tree.

(J.) Cherry (dec.) is one of the best of our native woods. It is much used for fine finish and for cabinet work, as it holds its shape well, if thoroughly seasoned, and takes a fine finish. Its grain is of fine, even texture, of reddish color, and often stained to imitate mahogany. When well ebonized, it cannot be distinguished from the genuine wood except by weight.

Cherry is used by pattern makers for parts of patterns which are to stand rough usage. The tree is found in all of the states east of Texas, and in the Mississippi valley, but it is becoming too scarce for common use.

(K.) Chestnut (dec.) is a soft, open-grained wood, adapted to use in exposed situations. It is used a great deal for inside finish, as it will take a fine polish, and as the figures formed by the grain make it a very handsome wood for the purpose.

Not being a strong wood, it will not stand a heavy strain, and will shrink and crack badly in drying.

(L.) Cypress (con.) is similar to cedar. It is one of our most durable woods, and perhaps the best we have for outside work. It is used extensively for shingles; roofs covered with cypress shingles have been known to last for more than seventy-five years. The wood is light, straight-grained, and soft; it is easily worked, and holds its shape well. It is to great extent taking the place of white pine in the manufacture of doors, sash, and blinds, and is considered by many to be equal, if not superior, to that wood. It is much used in building small boats, and for use in places where it will be exposed to dampness. Eaves, troughs, and tanks made of it give better satisfaction than those made of any other woods except redwood and cedar, which are the only woods having anti-decaying qualities equal to cypress.

Cypress may be obtained in boards of almost any dimensions, and if it were stronger and harder, it would be one of our best woods for framing and finishing. It is used for the latter purpose to a considerable extent, as it has a handsome grain, and will take a polish well; if thoroughly seasoned, it will hold its shape as well as any wood. If it is seasoned slowly, it does not crack to an appreciable extent, but if forced, it is apt to be filled with fine shakes. Sap is not considered a blemish.

Cypress grows in the swamps and along the rivers of the Southern states, the best of it coming from those bordering on the gulf.

(M.) Elm (dec.) is a moderately hard wood, difficult to split. It warps and checks to some extent in drying, but when well seasoned it holds its shape as well as most woods in common use. It is susceptible to a good polish, and is used a great deal for interior finish and furniture, as it takes a stain well. Much of the quartered oak used in the manufacture of cheap furniture grew upon an elm stump. It is used largely in cooperage, and stands contact with the soil satisfactorily.

The elm is found in nearly all parts of the United States, but is more abundant east of the Mississippi river.

(N.) Gum (dec.), or, as it is more generally known, sweet gum, is extensively used for interior finish upon the better class of buildings. It warps and shrinks badly unless thoroughly seasoned, in which condition it is a very satisfactory wood. It is tough and strong, cross-grained, and of fine texture; its color is a warm, reddish brown, and it finishes handsomely. The gum tree grows abundantly in the Southern states.

(O.) Hemlock (con.) is found in most of the Northern states, and is used for scantlings, rough boards, under floors, and for boarding preparatory to siding. It is a fairly durable wood, but splits easily, and is apt to be full of wind shakes. It holds nails firmly.

(P.) Hickory (dec.) is the hardest native wood in common use, and the toughest wood that we have; it is too hard to be used for building material. It is flexible, and its principal use is for wagon and carriage work, and for other purposes where bent wood and great strength is required. As it does not split easily, it is much used in the manufacture of tool handles. It is liable to attacks from boring insects, and these pests often destroy much valuable timber.

Sap is not considered a defect, and the sapwood is in fact the most desirable part of the tree, on account of its creamy whiteness and great strength.

(Q.) Locust (dec.) is found in nearly all parts of the country, and is a useful and durable wood. It is much used for fence posts and, in damp locations, for railway ties, and sometimes for furniture, as it has a yellowish brown color which takes a polish well.

(R.) Maple (dec.) is a heavy, strong wood, nearly white, with a yellow or brownish tinge. There are several kinds of maple, but the kind generally used for commercial purposes is the sugar or rock maple. It does not shrink excessively, seasons without serious checking, and from it a very fine surface for polishing may be obtained. It is much used in places where it is exposed to wear, as in floors, butchers’ tables, etc., and to a considerable extent as a cabinet wood, and for interior finish. Maple does not resist decay as well as do some other woods.

Sap is not considered a defect, and on account of its whiteness the sapwood is often preferred to the heartwood for many uses.

Bird’s-eye maple is of this wood, but some peculiarity in the growth of certain trees, believed by many to be caused by woodpeckers, has caused the tree to have what seem to be numerous small knots, known as curls or eyes. The presence of these imparts a beauty which is possessed by no other wood, and has never been successfully imitated.

(S.) Mahogany (dec.) is an imported wood, and is much used in the finish of fine buildings and in the manufacture of fine furniture. It is of a rich red color, and has a beautiful grain and other desirable qualities which make it the finest wood for finish in use. It holds its shape remarkably well, unless it is very cross-grained, and is in every respect an ideal cabinet wood. Its cost is all that prevents it from being universally used.

(T.) Oak (dec.) is our best all-round native wood. It is found abundantly in nearly all parts of the country, and forms the larger part of our broad-leaved forests. There are a number of species of oak, but they are in general known to commerce as the red and the white oak. Nearly all these trees are cut for commercial purposes, but the white oak is the finest. The wood of some varieties of oak is so similar to the white oak that the difference cannot be distinguished after the work is finished, therefore they are all put together and sold as a medium grade of white oak for purposes where the strength of the genuine is not required. This will generally account for the difference in the grain and the color which is noticed in handling the commercial white oak.

Red oak is a coarser wood, and is more apt to give trouble in seasoning than white oak, though they both have to be dried very carefully, or there may be checks and cracks to such an extent that the wood will be ruined. Both the red and the white oak are used extensively in finishing and cabinet work, but the red oak is used commonly upon the cheaper grades, as it is easier to work.

The two varieties should never be used upon the same job, unless the wood is to be stained a dark color, as there is a marked difference in their appearance when finished. White oak is much used for flooring, quartered oak resulting in a beautiful floor, if the work is well done.

Oak is not a suitable wood for exposure to trying climatic conditions, though if buried deeply, or in water, where there is no alteration in moisture or dryness, it gives satisfaction. White oak is used to great extent for railroad ties, but what these are to be made of in the future is causing much speculation, as the end of the present supply of white oak is already in sight.

(U.) Pine (con.) in its different varieties is used more than any other kind of wood. It is found in nearly all parts of the United States and in Canada. Certain sections of the country which were once covered with virgin pine forests have, however, been so denuded of their wealth, and so many of their young trees destroyed, within a few short years, by the depredations of lumbermen who cared more for their immediate profit than for the prospective good of the nation, that instead of a permanent and continual supply of this valuable wood, there are now nothing but barren hillsides, and the moss-grown ruins of the lumber camps and sawmills by means of which this irremediable wrong was perpetrated against posterity.

White pine is soft, easily worked, and when thoroughly seasoned will hold its shape better than any other wood except mahogany. For these reasons, and on account of its adaptability to gluing, it is used almost exclusively by pattern makers. It is found in the Northern states and in Canada. Farther south is the belt in which grows the grade of pine known as “Carolina,” the bastard or yellow pine. This belt extends from the Mississippi valley to the Atlantic coast, and is of a width to include Virginia and the Carolinas. This pine is harder to work, and has a more pronounced grain than has the white pine, but it makes a handsome wood for interior trim, as it is capable of a fine finish. Carolina pine is neither so hard nor so strong as “Georgia” pine, which is also known commercially as long-leaved pine, pitch pine, or hard pine. This wood is found from Virginia to Texas, in the states bordering upon the ocean and the gulf.

Pitch pine has a finer, closer grain than has either of the two above described, being much stronger and more dense. This is the wood which is used for heavy timbers of large buildings, and the above described grades should never be confused with it, the Carolina pine resulting in work of less strength, for instance, if used where the pitch pine was intended. Although this wood is very hard and strong, and is the best wood for heavy construction, as has been stated, it should never be used in any place which is not dry and well ventilated, as it will decay rapidly if placed in a damp location, or where it will come in contact with the earth.

Fig. 19.—White Pine Forest.

There are several varieties of pine besides those above mentioned. These are generally less desirable for finish or for construction than is the white, yellow, or Carolina pine, but they are used extensively for the common work of light building, and by box factories.

(V.) Poplar or whitewood (dec.) is cut from the tulip tree, and is found principally in the Middle West and in some parts of the South. It is of light weight and color, with few knots, and is soft and easily worked. It is used for the common grades of cabinet work, inside finishing, veranda posts, etc. It takes a stain remarkably well, and its even texture makes it a favorite with wood carvers. It warps and shrinks considerably in seasoning, and unless held in its place, it is apt to twist.

(W.) Redwood (con.) is taken from the big trees on the Pacific slope; it is straight-grained, soft, and free from knots, and may be obtained in boards of any size which it is possible to cut. It has the reputation of being one of the best woods for use in trying conditions, or where it will be exposed to alternations of dryness and moisture.

It has a very coarse grain and takes a finish well, but it is not apt to become very popular for inside finish, as it is easily marred, and, although very soft, will, when thoroughly dry, destroy the edge of tools quicker than many harder woods. It turns to a dull, unattractive brown as it ages, if it is finished in its natural color.

It is claimed by many to be the best wood for shingles, as it resists decay indefinitely. It shrinks both ways of the grain, and burns very slowly.

Fig. 20.—Douglas Spruce Forest.

(X.) Spruce (con.) is moderately hard and strong, and in New England is used generally for framing light buildings and for rough boarding. Its color is almost pure white, and it has the valuable quality of holding nails firmly. There is little difference between the heart and the sap wood, and its texture is sometimes such that it is difficult to distinguish it from white pine. It warps and twists badly in seasoning, and on that account is not suitable for framing trusses, unless seasoned lumber is used.

Spruce is used also for a cheap grade of clapboards, for flooring, ceiling, and laths, and also by paper pulp manufacturers in immense quantities. It is a fairly satisfactory wood for immersion, but if exposed to alternations of dryness and moisture, it decays rapidly.

(Y.) Sycamore, or buttonwood (dec.), is found in nearly all parts of the Mississippi valley and in the Eastern states. It is a moderately stiff and strong wood, coarse-grained, and quite difficult to smooth to a surface, as the grain seems to run in all directions at once. It has also a disagreeable habit of warping and twisting as it seasons, but if well seasoned and properly handled, it will give no more trouble than do other woods. It takes a good polish, and is a desirable wood for inside finish.

(Z.) Walnut, or black walnut (dec.), is found in all the Middle and Eastern states. It is heavy, firm, and strong, of a chocolate color, and takes a fine finish. It is well adapted to inside finish and to furniture work.

At one time nearly all the best work was done in this wood, but at present it is out of style, as oak and other woods are more in favor. Like other varieties of our best woods, this has been cut out, and is now too expensive to be considered as anything but a fancy wood.

White walnut is described under butternut.

Fig. 21.—Red Spruce and Balsam Fir Killed by Fire.

Suggestive Exercises

8. How are small lumbering operations conducted? Large operations? What is the favorite method of bringing logs to the mill? Why? Compare the circular and the band saw as to economy. Why is scientific forestry a necessity?

9. What are the usual thicknesses to which planks are sawed? How much thinner is dressed than sawed lumber? How are ½ boards usually sawed? How should a log be sawed to get the most out of it? To furnish dimension lumber? Describe the advantages and the methods of quarter-sawing. Compare plain and quarter-sawed lumber as to economy. Compare and give reasons for their different shrinking qualities. What are the different names by which quarter-sawed lumber is known?

10. Describe and demonstrate the four grades of lumber as they are commonly graded.

11. What will be the nature of the sound if a dry, perfect piece of timber is struck with the knuckles? A wet or decaying piece? What does it usually signify if there is a great variety of color in a board? How may decayed lumber be detected by its odor? How may incipient decay be stopped? How may decay be prevented or cured?

12. How is lumber less than 1” in thickness surveyed? Lumber over 1” in thickness? How are joists and scantlings measured? To what lengths are logs sawed in the forest? In surveying, where should a common board be measured? A quarter-sawed board? Demonstrate the use of the lumber scale.

13. What should be the qualities of a good framing timber? Of timber for outside finish? To be buried? For floors? For inside finish? For shingles? For siding? How long should lumber be dried before using? How should lumber for inside finish be cared for while waiting for use? Describe the qualities and the uses of the following kinds of lumber: ash, apple, basswood, beech, birch, butternut, cedar, cherry, chestnut, cypress, elm, hemlock, hickory, locust, maple, mahogany, oak, pine, poplar, spruce, sycamore, walnut.

CHAPTER III

Care of Lumber

14. The piling of lumber.—(A.) To the uninitiated it may seem that the piling of lumber is work upon which it is not necessary to expend much skill, but there are few operations in which carelessness or ignorance will cause more loss to a wood-worker.

(B.) The front end of a lumber pile should be higher than the back, therefore it is a good plan to locate it upon ground which falls away to the rear, or to build the ways which support the pile so that the water which drives into the pile will run out at the back end, and not stand upon the boards, as this will cause discolorations.

15. Permanent lumber ways.—These should be built by some method similar to that shown in Fig. 22. It is not a good plan to lay timbers upon the ground, as they will decay rapidly, and there will not be sufficient room for air to circulate under the pile to allow the boards of the lower courses to dry out properly. The pile is also apt to settle when the frost comes out of the ground in the spring. Lumber should not be stacked above wet or marshy ground; if necessary to stack it where the weeds are of rank growth, the latter should be kept down.

The ways should be built with a solid foundation, well below the frost line, though this is rarely done except for permanent lumber storage. This is shown at a, Fig. 22, in which it will be seen that the ways are built to stand a heavy load; the space between the centers of the ways should be about five feet, as multiples of this distance will accommodate any length of boards.

Fig. 22.—Permanent Lumber Ways.

16. To minimize the warping of lumber.—(A.) Do not place lumber piles less than one foot apart, as it is necessary that there should be a continuous circulation of air through the pile in all directions. (See b, Fig. 22.)

(B.) Lumber piles are usually four feet in width, and should be built up with sticks of that length, which are placed between the courses of boards. It is important that these be placed directly over each other and the ways; otherwise there will be short kinks in the boards, as shown at c. It is such carelessness as this that causes a great deal of loss. In piling very expensive lumber, the front sticks should be laid so as to project a little over the course of boards below, and the boards of the course above should project the same distance over the stick, in order to give the front of the pile an inclination to the front, as shown at d, which will allow most of the rain-water to drop clear of the boards below, instead of running down the front and finding its way into the pile.

(C.) Square piles are sometimes built, but in these the boards should be laid with large spaces between them, to allow perfect circulation of air. It is obvious that in a pile of this sort, the boards in the center of the pile will not come in contact with the air as much as those on the outside, and that consequently, unless carefully piled, the boards may be damaged by the moisture souring instead of drying out, which usually results in decay.

(D.) During the drying out process, all boards change their form more or less, depending upon the shape of the tree trunk, the kind and quality of the wood, the part of the tree from which the log was cut, as well as its size and age, the relation of the annual rings and medullary rays to the surfaces of the board, the length of time since the log was cut before being made into lumber, whether it had lain in water for several months, and the method of piling. Thus it will be seen that in every stage of preparing lumber for market, a high degree of skill and judgment is necessary to insure the best results.

Fig. 23.—Warping of
Lumber.

The greatest deterioration in lumber, after it has been cut and properly piled, is generally due to the tendency to warp, the cause of which is indicated in Fig. 23, and which may to great extent be minimized by skillful piling. If this sketch is studied carefully, it will be noticed that the middle board is thicker in the middle than it is at the edges, and that the curves of its top and bottom sides are practically uniform. This is because the annual layers are at nearly a right angle with the sides of the board, which causes the board to shrink in thickness, and very little in width. This is due to the tendency of lumber shrink around, or parallel with, the annual layers. This tendency also causes the star shakes, as at c, Fig. 3, which is because the inner layers of the log, being less than the outside layers in circumference, and less exposed to the dry air, do not shrink so fast nor so much. This tendency is again illustrated in Fig. 23, in which it will be seen that because the outer annual layers shrink faster, they cause the outside of the board, or the part which grew toward the outside of the tree, to become narrower, and to assume a concave shape, while the side nearer the center of the tree, or the inside of the board, becomes convex. This is also the reason why boards cut near the outside of the log will shrink in width more than those cut nearer the center, which shrink in thickness proportionately more than in width.

(E.) For the purpose of taking advantage of the tendency to warp, and applying it to its own remedy, boards should be piled with the side which grew nearer the center of the tree uppermost. This will help to correct the tendency of the board to warp, as explained above, as the side which would naturally assume the concave shape will be underneath, and less likely to warp than if it were uppermost. This is not generally observed in stacking common lumber, since it needs care and judgment to do it properly, but it should be done if valuable lumber is being handled.

Fig. 24.—Lumber piled in Double
Courses.

Boards of practically the same width, if less than 7” wide, are sometimes stacked in double courses, as shown in Fig. 24, the outside of the boards, or the sides which grew nearer the outside of the tree being placed together, thus allowing the inside of the boards, or the sides which grew toward the center of the tree, to receive more air than the sides which are placed together, and therefore to dry out faster, which will reduce the warping to a minimum. After a pile is completed, it should be covered with old boards to protect the top courses from the weather.

(F.) A pile of valuable lumber should be restacked every six or eight months, as the boards are apt to become discolored where the lumber sticks are placed; in this rehandling, the warped boards should be placed with the concave side underneath.

(G.) If lumber is cut in winter or midsummer, and properly cared for, it is not apt to be injured by any rain which may drive into the pile, if there is free circulation of air; nor is it so liable to decay as lumber which is cut at other times of the year.

17. Weather-dried lumber.—Lumber which has been dried in the stack out of doors is not dry enough for use in the manufacture of inside finish or furniture, as it has dried out only to the degree of moisture in the outside air. If it is then worked up and placed in an artificially heated house, the heat will cause more moisture to evaporate, the wood to shrink, and the joints to open. For material to be used in the frames of buildings, in wagons, or in other places where the greatest possible strength is required, not less than two years weather-drying is preferred, as the material retains its full strength.

18. Kiln-dried lumber.—Lumber for furniture or for inside finish should be seasoned by the process known as “kiln-drying.” This means that lumber is exposed to a temperature of from 120° to 200° F. by which the moisture is extracted and evaporated. Lumber thus treated is apt to be more or less weakened by the action of the heat upon the fibers of the wood, which causes thousands of minute fractures, and in many cases the life and the elasticity of the lumber is destroyed. The results of kiln-drying depend largely upon the kiln, and upon the skill with which the lumber is piled, the heat applied, and the rapidity of evaporation of the moisture regulated.

For these reasons, much kiln-dried lumber is suitable for use where but little strength is required and where the color and the grain are the important points to consider.

19. Moist air kilns.—(A.) There are two types of dry kilns in common use: the natural draft, or moist air, kilns, and the induced draft kilns. These two types are made by different manufacturers, nearly all of whom use certain devices of which they control the patents, and which constitute the chief difference between their kiln and those made by other manufacturers.

(B.) The moist air kilns are so constructed as to allow the freest possible circulation of the heated air, and to provide opportunities for the moisture to be expelled in accordance with certain natural laws, which results are obtained by a carefully planned and managed system of ventilation. These kilns operate upon the principle that heated air circulating naturally through lumber will become charged to a much greater degree with moisture than if it were forced through rapidly, as in the induced draft kilns. Thus, heated air by passing slowly through a pile of lumber may become charged with moisture nearly to the dew point.

If the humidity of the heated air is maintained at that point, by allowing the moisture to pass out as it accumulates, with a small amount of heated air, which is replaced with fresh air from the outside, it is claimed that the boards will dry out from their centers. (C.) As the warm, moist air which circulates through the pile will keep the outsides of the boards moist, it will prevent case hardening, or the hardening of the outsides of the boards. This is caused by very warm dry air, which “cooks,” or closes the pores of the surface of the boards, and this prevents the outsides from shrinking, while the insides will be so badly checked and discolored as to destroy the boards.

After the moisture is all out of the lumber, that held in suspension will gradually pass out of the kiln, and the air inside will become perfectly dry.

(D.) It is claimed that all kinds of lumber in common use may be put into this type of kiln perfectly green, except oak and other very hard woods, which should have at least thirty days’ drying under good drying conditions for each inch in thickness. It is also claimed that the moist air kiln is simply weather drying accelerated,—the moisture being thoroughly extracted from the lumber, the result being the same as though it were stacked out of doors for several years,—and that the lumber has lost none of its strength, elasticity, or characteristic color.

(E.) This method sometimes is applied by steam pipes extending between each course of boards, and in this way the lumber is dried out very rapidly. Lumber used in this sort of kiln should be thoroughly weather-dried, or otherwise the high temperature will cause it to check badly. In certain forms of these kilns, the lumber is saturated with live steam after it is piled in the kiln, before the heat is turned on.

20. Induced draft kilns.—(A.) This system of kiln-drying consists of a power-driven fan, which forces the heated air at a high rate of speed through the spaces between and around the lumber piled in the chamber.

(B.) Manufacturers have different devices for extracting the moisture from the air after it has passed through the lumber piles. It may be passed over condensing plates, or through coils of pipes in which cold water is continually circulating, both of these devices being for the purpose of extracting the moisture from the heated air. If the moisture is separated from the air by condensation, it runs away, but if not, a certain per cent of the heated air is expelled out of doors, being replaced by fresh air. The air in the kiln, somewhat cooled from contact with these cooled surfaces, is returned to the heater, reheated, and again forced through the kiln, which operation is repeated continuously and automatically. Thus the heated air becomes charged with a small percentage of moisture each time it passes through the kiln chamber; this moisture is extracted and the air is again heated before beginning another circuit, instead of slow circulation which allows the heated air to become saturated with moisture before it is discharged, as in the moist air kiln.

The induced draft dry kiln requires quite an expensive equipment, as the blower and the appliance which drive it are necessary in addition to the equipment of the kiln itself, which would be similar in either of the types of kiln described. Lumber to be dried in this form of kiln must be well weather-dried before it is exposed to the high temperature of the kiln.

21. Results of the two systems.—While it is not the province of this book to pass judgment upon the results of the different methods or forms of dry kilns, it is obvious that the induced draft kiln is the more expensive to operate, as the expense of running the blower is avoided in the moist air system. In this latter type of kiln the steam simply passes through the pipes, the condensation being returned to the boiler to be reheated, so the only expense is that of maintaining the fire to keep up a low pressure. In the daytime, or while the engine which furnishes the power for the plant is running, the kilns of either type may be heated by exhaust steam.

Many users of one or both systems seem satisfied with the results obtained from either, while others are decided in their preference.

22. Filling a kiln.—In doing this, care should be used that there is plenty of room for the air to circulate freely around and through the pile—not less than 3” between the edges of the boards horizontally and vertically, and one foot between the lumber and the wall or adjacent pile. Each course of boards should be so planned as to bring the same width over those of the course below, if possible, in order to keep a vertical air space through the pile. In some cases the kiln is filled by placing the boards edgeways.

23. Length of time lumber should be left in the kiln.—No one should undertake to operate a kiln unless he understands perfectly the particular make of the kiln that he is handling, for if the ventilation is not correctly regulated, the entire charge of the kiln may become mildewed, casehardened, checked, discolored, or dried unevenly. No rule can be given for the time which lumber should be left in the kiln, as it depends upon the condition of the lumber, temperature, kind of lumber, dimensions, and ventilation. Generally speaking, if the kiln is properly constructed and operated, from two to four days for each inch in thickness of soft wood, and from two to three times as long, at a lower temperature, for hard wood, is usually enough to extract the moisture. It is, however, best to allow the lumber to stay in the kiln, at a moderate temperature, from three days to two weeks after the moisture is extracted, in order to harden and cook the solids of the sap, as by so doing the lumber is not so liable to be influenced by moisture in the future; this is the effect that long weather-drying accomplishes.

24. The care of kiln-dried lumber.—It is a common mistake to allow lumber to lie in an open shed or other place where it will absorb moisture from the atmosphere, and still call it kiln-dried. Lumber of this sort should be kept in a place where heat can be applied in damp weather, and should be stacked in a close, compact pile, so as to prevent the air from coming in contact with it.

25. Steaming wood.—This process makes wood pliable, and adds to its durability by destroying the germs which may cause decay; it also neutralizes, to a great extent, the effect of the presence of sap. Steaming or immersing wood in boiling water minimizes its tendency to shrink and swell, and wood thus treated is not so apt to check in seasoning. Steamed wood loses some of its original strength on account of the effect of the high temperature upon the fibers.

26. Preserving wood.—In order to preserve wood, it is sometimes treated with creosote or other chemicals, which are forced into the wood at a sufficient pressure to cause them to permeate the wood thoroughly. This treatment enables the wood to resist better the elements and to keep away insects, which do a great deal of damage, frequently honeycombing the wood with holes, with little or no evidence of their presence upon the outside.

Suggestive Exercises

14. What are some of the results of piling lumber carelessly? Should the back and the front of the lumber pile be upon the same level? Why?

15. How should lumber ways be built? What kind of places should be avoided in seeking a location for lumber piles?

16. Should the piles be placed close to each other? How wide should the piles be made? What is the objection to a square pile? How thick should the lumber sticks be? How should they be placed? What is the result if they are not carefully placed? How should the sticks and the ends of the boards be placed at the front of the pile? Why? What causes lumber to warp? Describe methods of piling lumber to minimize warping. Should a lumber pile be allowed to stand indefinitely? What is the proper time to cut lumber? Does it injure lumber to allow a little rain to beat into the pile?

17. What is meant by weather-dried lumber? Why is it not suitable for furniture and for inside finish? How is this remedied? For what purposes is weather-dried lumber the best?

18. What is the chief objection to kiln-drying lumber?

19. What are the two methods of kiln-drying? Describe the principle of the moist air kiln. What is claimed of it? How should hard wood lumber be treated before being kiln-dried?

20. Describe the induced draft system. What devices are used to extract the moisture from the heated air? What are the main points of difference between the two systems?

21. What is the difference in the condition of lumber which may be put in the two forms of kilns? Which is the more expensive system to install and operate? How do users of the two systems compare them?

22. How should lumber be stacked in the kiln?

23. How long should lumber generally remain in the kiln to allow the moisture to be extracted? How long to insure most permanent results?

24. How should kiln-dried lumber be cared for?

25. What is the effect of steaming wood?

26. How is wood sometimes treated to preserve it from the elements and from insects?

CHAPTER IV

Tools