Carpentry for Boys / In a Simple Language, Including Chapters on Drawing, Laying Out Work, Designing and Architecture With 250 Original Illustrations

CHAPTER XX ON THE CONSTRUCTION OF JOINTS

In uniting two or more elements, some particular type of joint is necessary. In framing timbers, in making braces, in roof construction and supports, in floor beams, and in numerous other places, where strength is required, the workman should have at his command a knowledge of the most serviceable methods.

Illustrations can most forcibly convey the different types; but the sizes must be determined by the character of the material you are working with. Our aim is to give the idea involved, and the name by which each is known.

Fig. 292. Bridle Joints. Fig. 292. Bridle Joints.

Reference has been made in Chapter X, to certain forms of scarfing and lapping pieces. This chapter has to do with a variety of other structural forms, but principally with such as are used in heavy building work, and in cases where neither fish plates nor scarfing will answer the purpose.

Fig. 293.

Fig. 293. Spur Tenon.

Fig. 294.

Fig. 294. Saddle Joints.

Bridle Joints.—This is a form of joint where permanency is not desired, and where it is necessary to readily seat or unseat the vertical timber. It is also obvious that the socket for the upright is of such a character that it will not weaken it to any great extent.

Spur Tenon.—This tenon can be used in many places where the regular one is not available. This, like the preceding, is used where the parts are desired to be detachable, and the second form is one which is used in many structures.

Saddle Joint.—This is still another manner in which a quickly detachable joint can be constructed. The saddle may be mounted on the main base, or cut into the base piece. An infinite variety of forms of saddles are made, most of them being used in dock work, and for framing of that character where large timbers are used, as in the building of coal chutes, and the like.

Fig. 295.

Fig. 295. Joggle Joints.

Fig. 296.

Fig. 296. Framing Joints.

Joggle Joint.—This joint is used almost exclusively for brace work where great weight must be supported. The brace has a tenon, and the end must also be so arranged that it will have a direct bearing against the upright, which it braces and supports, or it may have two faces, as in the second figure, which is an exceedingly strong construction.

Fig. 297. Heel Joints. Fig. 297. Heel Joints.

Fig. 298. Stub Tenon. Fig. 298. Stub Tenon.

Framing Joints.—These are the simplest form in which two members are secured together. They are used almost wholly in rafter work, and have very few modifications. The depth of the cut, for the toe of the rafter, depends on the load to be carried, and also on the distance the end of the rafter is from the end of the horizontal member on which the rafter rests.

Heel Joints.—This is by far the most secure of the framing type of joints. This, if properly made, is much better than the construction shown in the previous illustration, but the difficulty is to make the rafter fit into the recesses properly. This is no excuse for failure to use, but it is on account of inability to make close fits that is accountable for lack of use. It will be seen that in case one of the heels rests against the recess, and the others do not, and the pressure is great, there is a liability to tear out the entire joint.

Fig. 299. Tusk Tenon. Fig. 299. Tusk Tenon.

Stub Tenon.—This is another form of tenon which is made and designed to be used where it is in close proximity to another tenon, or where the mortises, if made full size, will weaken the member. The long tusk can be shortened, to suit the place where it projects, and the stub tenon on each side of the tusk may be made very short, and one side longer than the other if necessary.

Tusk Tenon.—Two forms of tusk construction are given. Any number of forms have been devised, all for special purposes, and designed for different kinds of woods. These shown are particularly adapted for soft woods, and the principal feature that is valuable lies in the fact that they have a number of shoulders within the mortise, each of which, necessarily adds to the strength. It should be observed that in the construction of the tusk tenon, the greatest care must be taken to have it fit the mortise tightly, and this has reference to the bottom and shoulder ends as well.

Fig. 300. Double Tusk Tenon. Fig. 300. Double Tusk Tenon.

Double Tusk Tenons.—The distinguishing difference between this and the preceding is in the tusk, which in this form of construction goes through the upright member, and is held by a cross key. The double tusk is intended for hard woods, and it is regarded as the finest, as well as the strongest, joint known.

Cogged Joints.—This differs from the regular tenoning and mortising methods, principally because the groove or recess is in the form of an open gain. It is used where the member is to be inserted after the main structure is put together.

Fig. 301.

Fig. 301. Cogged Joints.

Fig. 302.

Fig. 302. Anchor Joint.

Anchor Joint.—This form of connection is designed for very large timbers, and where great care must be taken in making the parts fit together nicely, as everything depends on this. This style is never used where the angles are less than 45 degrees, and the depth of the gain in the timber receiving the brace is dependent on the thrust of the brace.

Fig. 303. Deep Anchor Joint. Fig. 303. Deep Anchor Joint.

The Deep Anchor Joint is an extension of the tongue of the Anchor tenon, so that it affords a greater support for the end thrust. To clearly distinguish between this and the preceding form, it might be said that the Anchor Joint is one designed to protect the member containing the gains, while the Deep Anchor Joint favors the brace, by giving it a greater power.

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