Practical Carpentry

PRACTICAL CARPENTRY The use of wood in building construction antedates the earliest period of human history, and has coincided with the entire progress of our race. Although in some types of modern buildings—particularly those of the industrial class—wood has been largely supplanted by stronger and more durable materials, such as steel and concrete, it still retains a position of primary importance in the design and construc tion of the average modern home; while the part it plays as an accessory in masonry, steel, and concrete construction renders absolutely necessary to the builder of the present day a knowledge of the structural applications of wood and the methods of its manipulation.

Fundamental Geometrical Forms While it is not essential for a man to have a thorough knowledge of geometry in order to be a good carpenter, yet none will deny that with a knowledge of the science he would be a more competent workman.

At the outset, therefore, we shall enter into some of the details of geometry that will be found of frequent application.

Geometry

is the science of magnitude.

Magnitude

has three dimensions : breadth and thickness.

A Point has position but not magnitude. Prac tically, it is represented by the smallest visible mark cr dot; but geometrically understood, it occupies no space. The extremities or ends of lines are points; and when two or more lines cross one another, the places that mark their intersection are also points.

A Line has length, without breadth or thick ness, and, consequently, a true geometrical line cannot be exhibited ; for however fine a line may be drawn it will always occupy a certain extent of space.

A Surface has length and breadth, but no thickness. For instance, a shadow gives a very good representation of a surface—its length and breadth can be measured ; but it has no depth or substance. The quantity of space contained in any plane surface is called its area.

A Plane is a flat surface, which will coincide with a straight line in every direction.

A Curved or uneven surface is one that will not coincide with a straight line in all directions.

By the term surface is generally understood the outside of any body or object.

A Solid is anyth ng which has length, breadth, and thickness; consequently the term may be applied to any visible object containing substance, but practically it is understood to signify the solid contents or measurements contained within the different surfaces of which any body is formed.

Lines

may be drawn in any direction, and are termed straight, curved, mixed, concave or con vex lines, according as they correspond to the following definitions :— A Straight Line is one every part of which lies in the same direction between its extremities,and is, of course, the shortest distance between two points.

A Curved Line

is such that it does not lie in a straight direction between its extremities, but is continually changing by inflection. It may be either regular or irregular.

A Mixed Line

is composed of straight and curved lines, connected in any form.

A Concave or Convex Line

is such that it can not be cut by a straight line in more than two points; the concave or hollow side is turned towards the straight line, while the convex or swelling side looks away from it. For instance, the inside of a basin is concave ; the outside of a ball is convex.

Parallel Straight Lines

have no inclination, but are everywhere at an equal distance from each other; consequently they can never meet, though produced or continued to infinity in either or both directions.

Oblique or Converging Lines

are straight lines which, if continued, being in the same plane, change their distance so as to meet or intersect each other.

An Angle

is formed by the inclination of two lines meeting in a point; the lines thus forming the angle are called the sides, and the point where the lines meet is called the vertex or angular point.

When an angle is expressed by three letters, as A B C, Fig. 1, the middle letter B should always denote the angular point.