Woodworking: Three Way Joints – Fixing Table Legs
Six ways of fixing legs at corners
Three-way joints are essential for making tables, chairs and certain types of framing. Construction methods range fromand screwing to dowelling or tenoning.
A simple way to join a leg to two rails  is by using a commercially produced corner plate which fits into slots in the rails a number of sizes are available. The joint holds together with alet through the plate into the leg. No other construction is needed.
Mark the positions of the legs and rails on the underside of the chair or table top. Cut the rails to the exact size. Position the plates at 45° in the corners on the pencilled outline and mark off where the slots which house the plates in the rails will be. Transfer these positions to the wood and cut the slots to fit.
Mark the inner corner of each leg where the plate-is to go, and drill a hole in it small enough for the pointed wood-screw end to bite firmly.
Fit the rails to the table top with shrinkage plates or small metal brackets, and slot in the corner plates; then drive a plate-screw into each leg. Insert the other end of the screw in the corner plate and tighten up the butterfly nut provided.
Dowels on corner joints  need to be staggered to prevent their meeting in the middle of the leg. Use at least three on each rail and space them evenly. The dowels should be one-third the thickness of the rails.
Glued-and-screwed corners are quick to make and quite strong. They can be arranged so that the leg is either inside  or outside the rails .
Countersink the screw heads well beneath the surface and fill the holes if the work is to be painted.
The strongest corner joint of all is the haunched and mitred mortise and tenon [5 and6]. Basically, the joint is just two haunched stub tenons meeting at right angles in the centre of the leg.
Mark out and cut the rails and both inner faces of the leg as for the haunched joint. Fit each rail separately, then mitre the ends of the tenons so that there is a small gap between them when the joint is assembled.
Leave about 15 mm. (1 in.) waste at the top of the leg, and trim it off when the joint is complete — this prevents splitting.
Where the leg is thick enough, haunched stub tenons will do. There is no need to continue the mortises through to meet each other.
For lightweight carcases, use loose-tongue joints, with ply or solid timber tongues let into solid corner-pieces and the ends of panels. The tongue should be one-third the thickness of the panel.
Tongues can also be cut oncorner-pieccs, as in wall cabinets or similar projects.