Carpentry for Boys Part 10

Read novel on https://www.novelall.com

[Ill.u.s.tration: _Fig. 193. Ogee-Reversa._]

[Ill.u.s.tration: _Fig. 194. Bead or Reedy._]

You will notice that the ogee is somewhat like the cymatium, the difference being that the concaved part is not so p.r.o.nounced as in the ogee, and the convexed portion bulges much further than in the ogee. It is capable of use with other moldings, and may be reversed with just as good effect as the ogee.

THE REEDY.--Fig. 194 represents the reedy, or the bead--that is, it is made up of reeds. It is a type of molding which should not be used with any other p.r.o.nounced type of molding.

THE CAs.e.m.e.nT (Fig. 195).--In this we have a form of molding used almost exclusively at the base of structures, such as columns, porticoes and like work.

[Ill.u.s.tration:_ Fig. 195. Cas.e.m.e.nt._]

Now, before proceeding to use these moldings, let us examine a Roman-Doric column, one of the most famous types of architecture produced. We shall see how the ancients combined moldings to produce grace, lights and shadows and artistic effects.

THE ROMAN-DORIC COLUMN.--In Fig. 196 is shown a Roman-Doric column, in which the cymatium, the ovolo, cavetto, astragal and the ogee are used, together with the fillets, bases and caps, and it is interesting to study this because of its beautiful proportions.

[Ill.u.s.tration: _Fig. 196._]

The pedestal and base are equal in vertical dimensions to the entablature and capital. The entablature is but slightly narrower than the pedestal; and the length of the column is, approximately, four times the height of the pedestal. The base of the shaft, while larger diametrically than the capital, is really shorter measured vertically.

There is a reason for this. The eye must travel a greater distance to reach the upper end of the shaft, and is also at a greater angle to that part of the shaft, hence it appears shorter, while it is in reality longer. For this reason a capital must be longer or taller than the base of a shaft, and it is also smaller in diameter.

It will be well to study the column not only on account of the wonderful blending of the various forms of moldings, but because it will impress you with a sense of proportions, and give you an idea of how simple lines may be employed to great advantage in all your work.

LESSONS FROM THE DORIC COLUMN.--As an example, suppose we take a plain cabinet, and endeavor to embellish it with the types of molding described, and you will see to what elaboration the operation may be carried.

APPLYING MOLDING.--Let Fig. 197 represent the front, top and bottom of our cabinet; and the first thing we shall do is to add a base (A) and a cap (B). Now, commencing at the top, suppose we utilize the simplest form of molding, the band.

This we may make of any desired width, as shown in Fig. 198. On this band we can apply the ogee type (Fig. 199) right side up.

But for variation we may decide to use the ogee reversed, as in Fig.

200. This will afford us something else to think about and will call upon our powers of initiative in order to finish off the lower margin or edge of the ogee reversa.

[Ill.u.s.tration: _Fig. 197._]

[Ill.u.s.tration: _Fig. 198._]

[Ill.u.s.tration: _Fig. 199._]

If we take the ogee recta, as shown in Fig. 201, we may use the cavetto, or the ovolo (Fig. 202); but if we use the ogee reversa we must use a convex molding like the cavetto at one base, and a convex molding, like the torus or the ovolo, at the other base.

In the latter (Fig. 202) four different moldings are used with the ogee as the princ.i.p.al structure.

BASE EMBELLISHMENTS.--In like manner (Fig. 204) the base may have the cas.e.m.e.nt type first attached in the corner, and then the ovolo, or the astragal added, as in Fig. 203.

[Ill.u.s.tration: _Fig. 200._]

[Ill.u.s.tration: _Fig. 201._]

[Ill.u.s.tration: _Fig. 202._]

STRAIGHT-FACED MOLDINGS.--Now let us carry the principle still further, and, instead of using various type of moldings, we will employ nothing but straight strips of wood. This treatment will soon indicate to you that the true mechanic or artisan is he who can take advantage of whatever he finds at hand.

Let us take the same cabinet front (Fig. 205), and below the cap (A) place a narrow strip (B), the lower corner of which has been chamfered off, as at C. Below the strip B is a thinner strip (D), vertically disposed, and about two-thirds its width. The lower corner of this is also chamfered, as at F. To finish, apply a small strip (G) in the corner, and you have an embellished top that has the appearance, from a short distance, of being made up of molding.

PLAIN MOLDED BASE.--The base may be treated in the same manner. The main strip (4) has its upper corner chamfered off, as at I, and on this is nailed a thin, narrow finis.h.i.+ng strip (J). The upper part or molded top, in this case, has eleven distinct lines, and the base has six lines. By experimenting you may soon put together the most available kinds of molding strips.

[Ill.u.s.tration: _Fig. 203._]

[Ill.u.s.tration: _Fig. 204._]

DIVERSIFIED USES.--For a great overhang you may use the cavetto, or the apophyges, and below that the astragal or the torus; and for the base the cas.e.m.e.nt is the most serviceable molding, and it may be finished off with the ovolo or the cymatium.

Pages of examples might be cited to show the variety and the diversification available with different types.

SHADOWS CAST BY MOLDINGS.--Always bear in mind that a curved surface makes a blended shadow. A straight, flat or plain surface does not, and it is for that reason the concaved and the convexed surfaces, brought out by moldings, become so important.

[Ill.u.s.tration: _Fig. 205._]

A little study and experimenting will soon teach you how a convex, a concave or a flat surface, and a corner or corners should be arranged relatively to each other; how much one should project beyond the other; and what the proportional widths of the different molding bands should be. An entire volume would scarcely exhaust this subject.

CHAPTER X

AN a.n.a.lYSIS OF TENONING, MORTISING, RABBETING AND BEADING

In the chapter on How Work is Laid Out, an example was given of the particular manner pursued in laying out mortises and tenons, and also dovetailed work. I deem it advisable to add some details to the subject, as well as to direct attention to some features which do not properly belong to the laying out of work.

WHERE MORTISES SHOULD BE USED.--Most important of all is a general idea of places and conditions under which mortises should be resorted to.

There are four ways in which different members may be secured to each other. First, by mortises and tenons; second, by a lap-and-b.u.t.t; third, by scarfing; and, fourth, by tonguing and grooving.

DEPTH OF MORTISES.--When a certain article is to be made, the first consideration is, how the joint or joints shall be made. The general rule for using the tenon and mortise is where two parts are joined wherein the grains of the two members run at right angles to each other, as in the following figure.

RULE FOR MORTISES.--Fig. 206 shows such an example. You will notice this in doors particularly, as an example of work.

[Ill.u.s.tration: _Fig. 206._]

[Ill.u.s.tration: _Fig. 207._]

The next consideration is, shall the mortises be cut entirely through the piece? This is answered by the query as to whether or not the end of the tenon will be exposed; and usually, if a smooth finish is required, the mortise should not go through the member. In a door, however, the tenons are exposed at the edges of the door, and are, therefore, seen, so that we must apply some other rule. The one universally adopted is, that where, as in a door stile, it is broad and comparatively thin, or where the member having the mortise in its edge is much thinner than its width, the mortise should go through from edge to edge.

The reason for this lies in the inability to sink the mortises through the stile (A, Fig. 207) perfectly true, and usually the job is turned out something like the ill.u.s.tration shows. The side of the rail (B) must be straight with the side of the stile. If the work is done by machinery it results in accuracy unattainable in hand work.

[Ill.u.s.tration: _Fig. 208._]

TRUE MORTISE WORK.--The essense of good joining work is the ability to sink the chisel true with the side of the member. More uneven work is produced by haste than by inability. The tendency of all beginners is to strike the chisel too hard, in order the more quickly to get down to the bottom of the mortise. Hence, bad work follows.

STEPS IN CUTTING MORTISES.--Examine Fig. 208, which, for convenience, gives six successive steps in making the mortise. The marks _a_, _b_ designate the limits, or the length, of the mortise. The chisel (C) is not started at the marking line (A), but at least an eighth of an inch from it. The first cut, as at B, gives a starting point for the next cut or placement of the chisel. When the second cut (B) has thus been made, the chisel should be turned around, as in dotted line _d_, position C, thereby making a finish cut down to the bottom of the mortise, line _e_, so that when the fourth cut has been made along line _f_, we are ready for the fifth cut, position C; then the sixth cut, position D, which leaves the mortise as shown at E. Then turn the chisel to the position shown at F, and cut down the last end of the mortise square, as shown in G, and clean out the mortise well before making the finis.h.i.+ng cuts on the marking lines (_a_, _b_). The particular reason for cleaning out the mortise before making the finish cuts is, that the corners of the mortise are used as fulcrums for the chisels, and the eighth of an inch stock still remaining protects the corners.