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The Practical Mechanic:
Every Man His Own Mechanic
Broken Window, How To Mend It
Knowledge Must Be Paid For
Kinds Of Woods Used In Carpentry
Toosl Used In Carpentry
The Glue Pot
The Carpenter's Bench
How To Hold And Handle Tools
Divisions Of The Building Trade
Soldering And Brazing
Indoor And Outdoor Painting
Varnishes And Recipers For Making Varnishes
Polishing And Recipes For Polish
Wall Paper Hanging
( Originally Published 1902 )
Of all the different kinds of wood, deal, or pine, is that with which the amateur will be most frequently employed, and of which it is most necessary that he should know the prices and sizes at and in which it can be procured at the timber yard. We shall now endeavor to convey some idea of the nature of a few common kinds of wood, and the purposes for which they are or may be used.
The Ash is a hardy deciduous tree, found generally in northern latitudes. In color the wood is greenish white when young, but the grain of timber cut from old trees is often dark and beautifully marked. When in this condition it is frequently used by the cabinet-maker. Its toughness, elasticity, and closeness of grain render the wood useful for making the frames of carriages, agricultural implements, felloes of wheels, etc. Hammer handles and billiard-cues are frequently made of Ash, as well as the handles of croquet-mallets, and it is much used by coopers. It admits of being bent almost double without snapping, and on that account it is well adapted to be used for curved work.
The BEECH, a hardy deciduous tree, is found in the northern States and Canada. The color varies; it is mostly light or whit-ish brown in tint, but is found in all shades of brown, deepening at times to black. The wood is fine and straight-grained, and is, in consequence, easily worked. The grain resembles that of mahogany, and it is often stained to represent it. It is used in the manufacture of furniture-tables, beds, and chairs being made of it. It may be stained to imitate ebony and rosewood.
The BIRCH is a forest tree of graceful appearance, found in cold and temperate regions, and on elevated situations, such as the sides of mountains in warmer countries. The wood is white, firm, and tough, and is used especially in northern countries for making wheels, casks and tubs, and in turnery.
The wood known as CHESTNUT is derived from two widely different kinds of trees-the Horse Chestnut and the Spanish or Sweet Chestnut. The white brittle wood of the Horse Chestnut is used by turners in making fancy goods. The wood of the Sweet, or Edible, Chestnut, is hard and durable, and beautifully grained and varie gated. Furniture is sometimes made of it, and it is used with effect for decorative purposes in building.
The name of PINE is given to the timber of a great variety of cone-bearing trees, although the deal or pine cut from different trees varies considerably in quality and general utility. It may be broadly distinguished as Red or Yellow Pine-for the names are indifferently used-and White Pine. In the one kind, the ground color of the wood is yellow, diversified with markings of pale red; in the other kind, the wood is of a whitish color, whence its name. The American White Pine is highly esteemed in carpentry work from its softness and the ease with which it can be worked. While not strong, it is durable. The difference in the two kinds of wood is this: the grain of the Yellow Pine is generally very straight and free from knots, and it is very durable, though it is soft and easily worked. This renders it peculiarly appropriate for all building purposes, whether in the construction of houses or ships. The great height and straightness of the pine renders it well suited for the masts of ships; and when stained and varnished the timber presents a handsome appearance for joiners' work in houses. White Pine is harder and not so straight-grained as Yellow Pine, and it is generally full of knots. The variety known as Silver Fir is used for flooring, and also in the manufacture of household furniture.
The OAK. The best Oak timber in the world is grown in America and Great Britain, from whose forests, until iron came so much into use for ship building. all the Oak was derived for the splendid fleets which have commanded the sovereignty of the seas. Although the grain is somewhat open-too open, indeed, for the purposes of the turner-the wood is extremely hard and durable, but difficult to work, and apt to take the edge pretty quickly off the workman's tools. The wood is dark in color and susceptible of a high polish. It is much used in house building, for houses of the better class, for floors, staircases, doors, the paneling of rooms, etc., and for tables, chairs, sideboards, and other pieces of household furniture.
The POPLAR. This wood is white, soft, and brittle, and is chiefly used in the manufacture of boxes, cases, and children's toys. The softness of the wood causes glass grinders and lapidaries to use horizontal sections as polishing wheels. The wood of the poplar is not liable to shrink, warp, or swell. The fret-sawyer will find it useful for backgrounds, linings, and veneered work.
The wood of the WALNUT is extremely useful and valuable, and is used in the arts for many purposes, of which not the least important is that of the manufacture of ornamental furniture. Its only drawback is its want of density, which renders it liable to injury from blows and rough usage. It is as useful to the turner as to the cabinet-maker, and works well in the lathe. It is desirable to get walnut wood from old, well-grown trees, for the older the tree the more beautiful and diversified are the markings of the wood.
For fret-sawing and all kinds of cabinet work, the wood known as BLACK WALNUT is the most suitable. Unless well seasoned by kiln-drying, or some similar process, it is apt to warp and split. It will take a beautiful polish, and still look well. Plain oiling seems to harden the fibre, and a dead polish will often show better in the work than though it shone like a mirror. This wood ought never to be varnished, since this gives a common look to the article, as it always brings out the grain.
The WHITE WALNUT, known in the United States as the buffernut, is a pretty wood, but soft. It cuts clean, and is adapted for many kinds of work, which, however, must not be delicate in design. It has the same grain as Black Walnut, stains well, and shows oiling to advantage.
Strength and Breaking Strain.
The most important qualities of building material necessary to consider are its strength and breaking strain or breaking weight, and the amount of pressure which can be safely laid upon it in accordance with its form, thickness, position, etc. It has been ascertained by actual experiments that the strength of a beam or girder of timber, and hence of any piece of timber, whether large or small, increases directly as the width, and as the square of the depth. Thus, if a piece of wood measuring three inches in breadth and three inches in depth-that is to say, nine inches square in section-will bear a certain weight, a beam six inches broad and three inches deep will bear twice the weight; but a beam three inches broad and six inches deep will bear four times the weight. The strength is also inversely as the length. If two beams of equal breadth and depth be taken, but one of them be twice as long as the other, the longer beam will only bear half the breaking weight that the shorter one will sustain, or, in other words, will be only half as strong.
It will now be clear why, in laying joists to sustain a floor, the timbers are so placed as to have considerable depth from top to bottom, while the breadth is comparatively narrow.
A continued strain tends to weaken the power of resistance in a beam, and the power will be lessened still more when the weight is variable, or is a rolling instead of a dead weight. The nature of the wood must also be taken into account: thus, some in which the fibre is long and the grain straight will bend to a very great degree, while others in which the grain is short and close will scarcely bend at all, but break suddenly. In framing timber, as the carpenter is called upon to do, all these points must be taken into consideration.
The instantaneous breaking weight of any kind of wood is the weight under which it will give way and break when loaded with the weight in the centre. It has been said that the load with which a beam may be weighted without risk should never exceed more than one-third of the breaking weight; but it is better and safer never to let the load exceed one fourth of the breaking weight. Indeed, it is argued that timber is permanently injured if more than this is applied to it. The best authorities on carpentry say that a load cannot be looked on as safe if it exceeds one-fifth part of the breaking weight.
It is by no means a difficult thing to find the breaking weight of every piece of timber, and, this being known, the load that it will sustain without injury; this as it has just been shown, estimated by different authorities at from one-fifth to one-third of the breaking weight. The following is a general rule for finding the breaking weight in the middle for girders of wood supported at both ends:
RULE.-Multiply the breadth in inches by the square of the depth in inches, and divide by the length of bearing in feet. The result obtained, when multiplied by a certain conslant or invariable quantity, for the kind of limber under consideration, gives the breaking weight in the centre in hundredweights.
This constant or invariable quantity, which has been determined by a series of experiments, is stated by Barlow to be: For Ash, 6 ; for Oak, 5 ; for Pitch Pine, 5 ; for Red Pine, 4 ; for White Pine, 3.