Woodworking joints – Angle joints (Part 3)
The Tusk Tenon
Another type of mortice and tenon joint used is the Tusk tenon. Arranged to weaken the timbers as little as possible, the tusk tenon is used in floor and roof construction. The tenon – which usually has a thickness of one-sixth the width of the material – is strengthened by projections left on the shoulder. The tenon projects through the timber that it is being jointed to and is secured with a wedge or key. A vertical section and plan are shown below (Fig A), and an isometric view (Fig. B). The tusk tenon, although not used as commonly as it once was (due to the likes of joist hangers), can still be found in floor joists.
- The wedge or key
- The tenon
- The tusk
Sometimes used for corner posts in lantern light windows, the Box tenon (Fig. C) is more complex to make than it looks. The easiest way of cutting the tenon is to cut using a tenon saw, giving, infact, three separate tenons.
The Tease tenon (Fig. D) is used when two rails are at right angles to each other in a corner post Z. The tenon on the piece X has the top part removed, whilst the piece marked Y has part of the bottom removed. The tenons pass over each other and may be also be wedged. When it is required that the tenons shall not be seen from the outside, then the tenons are kept to the full width and mitred at the ends.
A Chase mortice (Fig. E) is an ordinary mortice for a stub tenon, but the mortice is continued with a chase so that the rail can be swung round into the mortice. It is used for placing intermediate members into position after the framing has already been fixed. One end of the timber is fixed into postion using a normal stub tenon and then the other end is slid into position along the chase.
The Bridle joint
The Bridle joint is basically the reverse of the mortice and tenon joint. In bridle joints, the middle part of one piece of timber is cut out so it will fork on to the other timber, which is cut to receive it.The two pictures below show bridle joints for when the two timbers are at right angles to each other (Fig. E) and also the type of bridle joint that could be used in roofing work where the two timbers meet at an angle.(Fig. F).
Notched and cogged joints
Notched joints are similar to halving joints, except that the faces of the two pieces are not flush. A straight forward notched joint is shown below (Fig. G), whilst a notched joint that prevents the movement of both pieces (Fig H) is also shown. A Cogged joint (Fig.I) is an extension of both the notched joints shown and is prevents movement of both timbers.
The Bird’s mouth joint (Fig. J) is used for timbers that are not in the same plane. A common example can be found in a traditional cut roof, between the foot of the common rafter and the wall plate.
This finishes our look at angle joints; our next post will be looking at joints for joining timber in length.