Carpentry for Boys Part 17

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In order to familiarize the boy with the different terms used in a plane, examine Figure 277. The parts are designated as follows: 1A is the double plane iron; 1 single plane iron; 2 plane iron cap; 3 cap screw; 4 lever cap; 5 lever cap screw; 6 frog complete; 7 Y adjusting lever; 8 adjusting nut; 9 lateral adjusting lever; 11 plane handle; 12 plane k.n.o.b; 13 handle bolt and nut; 14 k.n.o.b bolt and nut; 15 plane handle screw; 16 plane bottom; 44 frog pin; 45 frog clamping screw; 46 frog adjusting screw.

[Ill.u.s.tration: _Fig. 277. Details of Metal Plane._]

RABBETING, MATCHING AND DADO PLANES.--Figure 278 shows a useful form of plane for the reason that it is designed to receive a variety of irons, adapted to cut rabbets.

The detached sections of Fig. 278 show the various parts, as well as the bits which belong to it. 1, 1 represent the single plane irons; 4 the lever cap; 16 the plane bottom, 50 the fence; 51 the fence thumb screw; 61 the short arm; 70 the adjustable depth gage; 71 the depth gage which goes through the screw; and 85 the spurs with screws.

MOLDING AND BEADING PLANE.--A plane of the character shown in Fig. 279 will do an immense variety of work in molding, beading and dado work, and is equally well adapted for rabbeting, for filletsters and for match planing. The regular equipment with this tool comprises fifty-two cutters.

[Ill.u.s.tration: _Fig. 278. Rabbet, Matching and Dado Plane._]

As shown in Fig. 279, the plane has a main stock (A), which carries the cutter adjustment, a handle, a depth gage, a slitting gage, and a steel bottom forming a bearing for the other end of the cutter, and slides on arms secured to the main stock.

This bottom can be raised or lowered, so that, in addition to allowing the use of cutters of different widths, cutters can be used having one edge higher or lower than the edge supported in the main stock.

[Ill.u.s.tration: _Fig. 279. Molding and Beading Plane._]

The auxiliary center bottom (C), which can be adjusted for width or depth, fulfils the requirement of preventing the plane from tilting and gouging the work. The fence D has a lateral adjustment by means of a screw, for extra fine work. The four small cuts in the corners show how the bottoms should be set for different forms of cutters, and the great importance of having the fences adjusted so that the cutters will not run.

The samples of work ill.u.s.trated show some of the moldings which can be turned out with the plane.

[Ill.u.s.tration: _Fig. 280. Dovetail Tongue and Groove Plane._]

DOVETAIL TONGUE AND GROOVE PLANE.--This is a very novel tool, and has many features to recommend it. Figure 280 shows its form, and how it is used. It is designed to make the dovetailed tongue as well as the groove.

It will cut any size groove and tongues to fit with sides of twenty degrees flare, where the width of the neck is more than one-quarter of an inch thick, and the depth of the groove not more than three-quarters of an inch. The tongue and groove are cut separately, and can be made with parallel or tapering sides. The operation of the plane is very simple.

[Ill.u.s.tration: _Fig. 281. Fig. 282. Router Planes._]

ROUTER PLANES.--This is a type of plane used for surfacing the bottom of grooves or other depressions parallel with the general surface of the work.

The planes are made in two types, one, like Fig. 281, which has a closed throat, and the other, Fig. 282, with an open throat. Both are serviceable, but the latter is preferable. These planes will level off bottoms of depression, very accurately, and the tool is not an expensive one.

DOOR TRIM PLANE.--This is a tool for making mortises for b.u.t.ts, face plates, strike plates, escutcheons, and the like, up to a depth of 5/16, and a width of 3 inches. The princ.i.p.al feature in the plane is the method of mounting the cutter, which can be instantly set to work from either end of the plane or across it.

[Ill.u.s.tration: _Fig. 283. Door Trim Plane._]

The cutter, as shown in Fig. 283, is cushioned by a spring which prevents taking a heavier chip than can be easily carried. A fence regulates the position of the cut and insures the sides of the cut being parallel. The depth of the cut is governed by a positive stop. By removing the fence and locking the cutter post with the thumb screw, instead of using the spring, a very superior router plane is obtained.

CHAPTER XIX

ROOFING TRUSSES

The chapter on Bridge Building gives some suggestions as to form of trusses, the particular types there shown being princ.i.p.ally for wide spans. Such trusses were made for one purpose only, namely, to take great weight, and they were, as a consequence, so constructed as to provide strength.

But a roofing truss, while designed to hold the acc.u.mulated materials, such as snow and ice, likely to be deposited there, is of such a design, princ.i.p.ally, so as to afford means of ornamentation. This remark has reference to such types as dispense with the cross, or tie beam, which is the distinguishing feature in bridge building.

The tie beam is also an important element in many types of trusses, where ornamentation is not required, or in such structures as have the roofed portion of the buildings enclosed by ceiling walls, or where the s.p.a.ce between the roofs is used for storage purposes.

In England, and on the Continent of Europe, are thousands of trusses structured to support the roofs, which are marvels of beauty. Some of them are bewildering in their formation. The moldings, beaded surfaces, and the carved outlines of the soffits, of the arches, and of the purlins, are wonderful in detail.

The wooden roof of Westminster Hall, while very simple in structure, as compared with many others, looks like an intricate maze of beams, struts and braces, but it is, nevertheless, so harmonized that the effect is most pleasing to the eye, and its very appearance gives the impression of grandeur and strength.

Nearly all of the forms shown herein have come down to us from mediaeval times, when more stress was laid on wooden structures than at the present time, but most of the stone and metal buildings grew out of the wooden prototypes.

Now the prime object of nearly all the double-roofed trusses was to utilize the s.p.a.ce between the rafters so as to give height and majesty to the interior.

A large dome is grand, owing to its great simplicity, but the same plain outlines, or lack of ornamentation, in the ceiling of a square or rectangular building would be painful to view, hence, the braces, beams, plates, and various supports of the roofed truss served as ornamental parts, and it is in this particular that the art of the designer finds his inspiration.

Before proceeding to apply the matter of ornamentation, it might be well to develop these roof forms, starting with the old type Barn Roof, where the s.p.a.ce between the rafters must be utilized for the storage of hay.

[Ill.u.s.tration: _Fig. 284. Gambrel Roof._]

_The Gambrel Roof_, Fig. 284, requires a tie beam, (A), as shown, but the s.p.a.ce above the beam is free of all obstructions, and gives a large storage s.p.a.ce. The roof has two sets of rafters (B, C), and of different pitch, the lower rafters (B) having a pitch of about 30 degrees, and the upper ones (C), about 45 degrees.

A tie bar (D) joins the middle portion of each of the rafters (B, C) and another tie bar (E) joins the middle part of the rafter (B), and the supporting post (F). The cross tie beam (G) completes the span, and a little study will show the complete interdependence of one piece upon the other.

[Ill.u.s.tration: _Fig. 285. Purlin Roof._]

_The Purlin Roof_ is a type of structure used very largely throughout the United States, for wide barns. (A) is the cross beam; (B, B) the purlin posts; (C, C) the purlin plates; (D, D) the rafters; and (E, E) the supporting braces.

The rafters (D) are in two sections, the distance from the eaves to the comb being too great for single length rafters, and the purlin plates are not designed to make what is called a "self-supporting" roof, but merely to serve as supports for the regular rafters.

_The Princess Truss_, on the other hand, is designed to act as a support for the different lengths of rafters (A, B, C), and as a means for holding the roof. It is adapted for low pitch and wide spans.

[Ill.u.s.tration: _Fig. 286. Princess Truss._]

The main truss is made up of the cross beam (D), rafters (E, E) and thrust beam (F). Purlin posts (G, G) are placed at an angle intermediate the ends of the rafters, and the purlin plates (H, H) support the roof rafters (A, B, C); I, I are the vertical tie rods.

This type is probably the oldest form of truss for building purposes, and it has been modified in many ways, the most usual modification being the subst.i.tution of posts for the tie rods (I, I).

Following out the foregoing forms, we may call attention to one more type which permitted ornamentation to a considerable degree, although it still required the tie beam. In fact the tie beam itself was the feature on which the architect depended to make the greatest effect by elaborating it.

This is shown in Fig. 287, and is called the _Arched_, or _Cambered, Tie Beam Truss_. It is a very old type, samples of which have been found which take it back to a very remote age.

[Ill.u.s.tration: _Fig. 287. Arched, or Cambered, Tie Beam._]

The tie beam A, in wide spans, was made in two sections, properly tied together, and sometimes the outer ends were very wide, and to add to the effect of the arch, it might also be raised in the middle, something in the form shown by the dotted line (B).

_The Mansard_ is what may be called a double-mounted roof, and it will be seen how it was evolved from the preceding types. It will be noted that the simple truss formed by the members (A, B, C) is merely superposed on the leaning posts, the tie beam also being necessary in this construction.

[Ill.u.s.tration: _Fig. 288. The Mansard._]

But the most elaborate formations are those which were intended to provide trusses for buildings wherein the tie beams were dispensed with.