[Fig. 216] is a scarfed joint with undercut vee'd ends which prevent the joint from lipping up or down or sideways. It is a useful joint, calling for careful setting out and accurate craftsmanship. Folding wedges are used in this case to draw up and secure the joint.
[Fig. 217] is a "fished joint," and the following difference between a scarfed and fished joint should be noted. A fished joint need not necessarily reduce the total length of the beams to be joined, and fish plates of wood or iron (or a combination of both) are fastened at each side of the joint. In a scarf joint all surfaces are flush. In [Fig. 217] the beams are butt-jointed and secured by wooden plates and iron bolts. The upper plate is let into each beam, and the lower plate is provided with two wooden keys to prevent the beams sliding (or "creeping") upon the lower plate. Iron nuts, bolts, and washers are used to complete the joint.
Fig. 217.—Fished Joint.
In the case of the scarfed joint at [Fig. 218] (used for purlins) the length of the scarf is usually made about four times that of the depth of tie beam. It has two hardwood keys which force the pieces together and thus tighten the joint.
Fig. 218.—Detail of Scarfed Joint in Purlins.
The methods of scarfing and fish-jointing are many and varied, and, in selecting a joint, the nature of the pieces to be joined and the direction and the amount of the load should be carefully taken into consideration.