From DIYinfo.org
Marking up the pieces
On rough-sawn wood you can mark out the cutting lines in pencil, but for hardwood or softwood furniture you should scribe the lines with a marking knife held carefully against the side of a try square. Bear in mind that the knife leaves quite deep marks in the wood, so mark heavily only the areas you intend to cut or you will spoil the finished appearance of the halving joint.
[edit] Tee halving joint
The procedure for marking up a tee halving joint is as follows:
Where halving joints are to be fitted in pairs, be sure to mark up each pair of pieces at the same time to make certain that they come out to the same length (fig. 1).
Mark the width of the cross-rail across the face of the side rail and half way down both edges.
Mark the shoulder line across the back of the cross-rail at a distance from the end about 6 mm longer than the width of the side rail (fig. 2). Continue this line across the edges of the wood.
Set a marking gauge to half the thickness of the pieces of timber. Scribe a short test line on one of the edges, then turn the gauge around and mark the same surface from the other side. If the two marks merge into one, the gauge is set. If not, adjust it until they do.
With the gauge set correctly, scribe depth lines for the socket part of the joint on both edges of the side rail (fig. 3).
Gauge the thickness of the pin along the edges, and across the end of the cross rail, then mark the waste area on both pieces (fig. 4).
[edit] Sawing the pin
When sawing the section out of the cross rail to form the pin of a tee halving joint, the 'rip' cut that runs in the same direction as the grain must be made before the cross cut across the grain.
Place the wood vertically in the vice, in a low position to prevent vibrations that might-cause the saw to jump off the wood.
Using a tenon saw (hacksaw), notch the corner of the wood on the waste side at the far side of the gauge line by drawing the blade of the saw back (fig. 5).
Use your thumb to guide the blade and continue sawing gently, letting the saw handle drop slowly until the blade is in the horizontal plane.
When you have cut a groove about 5 mm deep in the end of the wood, saw down to the shoulder line on one side of the piece (fig. 6).
Afterwards, reverse the wood and, remembering that the waste will have changed sides, saw down to the shoulder line on the other side (fig. 7).
Finally, hold the wood vertically in the vice once more and saw out the V-shaped piece of wood left inside the cut (fig. 8).
To make the cross cut, hold the wood on a bench hook and, cutting to the waste side, remove the waste wood with a tenon saw, taking care not to cut into, and weaken, the neck of the pin (fig. 9).
Finish off by clamping the wood horizontally in the vice and cleaning out the angle of the L-shaped cut with a chisel, paring across the grain (fig. 10).
[edit] Cutting the socket
When you have completed the pin section of the joint, hold it temporarily in place on the marked up side rail to make certain that the measurements for the socket are accurate.
Make minor adjustments if necessary. Secure the wood horizontally in the vice and make a saw cut, slightly to the waste side of each width line, down to the depth line.
Pare out the waste with a bevel edged chisel. Mark up and cut the pins for corner halvings and the sockets for cross halvings as described above.
[edit] Assembling the joint
When you come to assemble the members of a tee halving, you may find that the fit is too tight. In this case, plane a shaving off the edge of the pin rather than trimming the side of the socket.
In addition, you may find that the pin does not bed down sufficiently to produce a flush surface.
If this is the case, check that the bottom of the socket and the cut face of the pin are flat. If they are not, use a wide chisel or a flat file to level them.
Bear in mind that the joint should, as far as possible, be assembled only once before gluing in place: too many trial assemblies loosen the parts.
Before gluing the joint, cut off the excess wood at the end of the pin (fig. 11).
Apply a liberal amount of PVA adhesive to both surfaces to be joined and cramp the joint. To avoid marking the wood, pad the jaws of the cramp with timber off cuts.
Before the glue sets, check again that the joint is tight fitting and wipe off any excess adhesive with a damp cloth. Tee halving joints should be given extra strength by nails or screws (see Nailing Tips), or if a particularly rigid joint is required you can drill through the joint and secure it with a glued dowel peg (fig. 13).
[edit] Dovetail halving joints
Although more complicated to construct than the tee halving, the dovetail halving is a useful joint because it can withstand sideways tension without being screwed or pegged. Although the construction technique is similar to that for a tee halving, the marking up procedure and the order of cutting are quite different:
1. Mark out the shoulder line of the pin around the piece of wood with a try square and marking knife.
2. Mark up the sloping lines of the dovetail, using a sliding bevel to obtain an equal angle on both sides of the wood (fig. 14).
3. Use the marking gauge to mark the halving lines as above, and pencil mark all the waste areas. Position the wood in the vice at such an angle that one of the sloping lines is in the vertical plane.
4. Using the tenon saw, saw down the first sloping line to the shoulder mark (fig. 15).
5. Reposition the wood in the vice so that the second line is now vertical and saw down this line.
6. Saw down the halving line as described above.
7. With the wood held horizontally in the vice cut away the wide shoulder and the two short side shoulders with a tenon saw (fig. 17).
8. Clean up the edges and corners of the halved dovetail with a bevel edged chisel.
9. To mark up the shape of the socket section of the joint, place the pin over the other piece of wood and trace the shape of the pin onto the wood with a marking knife (fig. 18).
10. Use the marking gauge to score the halving lines onto the edges of the wood and pare out the waste as described above.
