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.
This is effected by joining the ends of boards already glued up with a piece called a clamp, which is secured by means of a groove sunk in it and a tongue cut across the fibres of the boards, these being often tenoned as well to fit into mortises in the clamp. In other instances the clamp is tongued and the boards cross grooved. The mitre clamped joint occurs when the ends of the clamp are mitred, as shown in Fig. 103. The object of the clamp in each case is to prevent the boards from casting and to give a more finished appearance. A joint between floor boards is also clamped when forced close with a flooring clamp or cramp, these two terms being now interchangeable and constantly used the one for the other.
This signifies one without any appreciable gape or crevice. Floors are laid with close joints, and in good work they should not open 1/16 in. within a year of being laid. The same rule applies to all other joiners' work not glued up, and where the deals used have been quite dry there will be much less shrinkage than that named within the same period.
This is one tightened up by means of a screw cramp or clamp, and it is to be observed that the terms cramp and clamp are and may be indiscriminately used for the tool employed to compress joints as well as for a piece fitted to prevent casting as above described.
Cross Grooved and Tongued Joint is made when a groove is cut out across the grain, as in heading and cistern joints, etc.
This is adapted for hinging together two stiles, and is illustrated in Fig. 104.
This is shown in Fig. 95, but it need not be grooved and tongued, nor must it of necessity be formed at an angle. When it is, and the angle happens to be a right angle, the bead is three-quarters of a cylinder, but when the angle is obtuse the bead is less. By beading matched boarding, rebated boarding, panelling, etc, the visible joint becomes a bead and double quirk, which is likewise well shown in Fig. 104. Double Tongued Joint is shown in Fig. 105. The same principle can be extended easily to more complex sections, but as a rule in the matter of joints utility and complication are in inverse proportion. Dovetail Joint. - This is not much used in joinery excepting for dovetailed backings to door linings, etc, shelving, drawers, etc. It is necessary that the fibres of pieces thus united should run parallel, so that pin and socket may contract or swell equally. In the common dovetail the dovetail appears on both sides of the angle. Fig. 116 shows the lapped dovetail.