This section is from the book "A Practical Treatise On The Joints Made And Used By Builders", by Wyvill J. Christy. Also available from Amazon: Practical treatise on the joints made and used by builders.
A description of halving in which a dovetailed notch is formed to prevent drawing, but which is untrustworthy for connecting ties. Timber shrinks about 2 per cent, in width and thickness, and consequently the dovetail in time withdraws from the cheeks of the notch and looseness ensues, which might work much mischief in some situations through the wedge-like shape and action of the dovetailed abutment of the tie. On the other hand, for struts, as in Fig. 34, the dovetailed notch is both suitable and picturesque, yet, at the same time, if the stress bo considerable, it is not advisable to employ it for the reasons given under Strut Joint.
Feather Wedged Joint is the same as Fox Wedged Joint.
This is used for joining timbers in the direction of their length, and is formed by butting the square ends of two pieces together and placing short pieces of timber or iron, Fig. 35, usually of the same depth, and called fishing or fish plates or pieces, midway over the butt joint on opposite sides and bolting the whole firmly together. When of wood, the fish plates are sometimes tabled to the main pieces. If intended to resist a compressive stress, plates on all four sides are necessary, and so are straps or hoops if a transverse one has to be borne.
A mode of securing a tenon against drawing or the action of a tensile stress in a mortise that is not cut through, as shown in Fig. 36, by placing one or more thin wedges of straight-grained wood into saw cuts at the end of the tenon. On driving the tenon home, as soon as the wedges touch the bottom of the mortise, which is slightly dovetailed or widened out, they split the tenon and compress it tightly home against the sides of the mortise. The more numerous and thinner the wedges are, the less chance is there of the tenon splitting up to its root.
Framed Joint is one made with a mortise and tenon.
This is explained in Section VIII. Sheet piling is sometimes run with a groove 1½ in. wide and 1 in. deep to receive a tongue of hard wood the same width and double the depth, which is nailed to one of the grooves to stand out an inch, but if the piles are carefully fitted before driving, they will come into close contact when driven, and the swelling of the wood exposed to moisture will form a tight joint. There are, however, some cases when angular grooving or grooving and tonguing, as above explained, is highly desirable, and doubtless in some instances strong tongues between heavy submerged timbers assist caulking in keeping out water, and have proved more than once a source of consolation to the engineer. The floors of bridges formed out of strong timber planking should be tongued and grooved with tongues about 1¼ in. wide, and well caulked.