Woodworking: Housing Joints and Tenon Joints

Housing joints

The housing joint is the classic way of joining a board end-on to an upright. The housing, or cut-out, gives accuracy of assembly and great load-bearing strength.

There are two main types: the through-housing, in which the cut-out continues right across the upright, and the stopped housing, which neatly conceals its own construction on the front.

Both types can be dovetailed by cutting one side of the housing, and an end edge of the cross-member, at an inward-sloping angle.

The stopped housing is the better job for display and cabinet work.

Through-housing

To make a through-housing, mark a line joint square across the inner face of the upright, hold the cross-member against the line, and scribe another line against it to give the exact width of the housing.

Continue these lines square across both edges of the upright. Set a gauge to the depth of the housing — usually one-third of the upright’s thickness — and gauge the depth line from the face side on both edges.

Cut down carefully to depth on both sides of the housing with a tenon or dovetail saw.

On long cuts, run the saw against a guiding batten clamped in place.

Chisel away the waste from each edge, beginning with gentle 30° cuts. Gradually reduce the paring angle until the centre is chiselled away. Finish the cut with a hand router. If you do not have one, take extra care with the paring, and check frequently with a straight-edge for constant depth and flatness.

Cut the cross-member to length. Plane the end square, preferably on a shooting board, and fit the joint. After gluing and pinning, plane the front and back edges to a flush finish.

Stopped housing

The construction is similar to that of a through-housing except that the cut-out ends about 18 mm. (¾ in.) from the front edge of the upright. The cross-member’s front corner is cut away to overlap this.

Scribe the upright as for the through-housing, but leave the front edge unmarked. Mark the stopped end of the housing with a gauge from the front edge.

You cannot saw to depth unless you clear away a space for the front of the saw to move in, so chisel out 40-50 mm. (1-1/2- 2 in.) from the stopped end to near the correct depth. Then saw to depth from the back edge on both sides, again using a saw guide on longer work.

Chisel away the waste and clean out to depth with a router.

On the cross-member, mark the cut-out to the depth of the housing and the length of the overlap. Saw away the waste with a tenon saw. There is no need for the cutout if the cross-member is designed to be set back from the front of the upright — just butt it against the end of the housing.

Through mortise and tenon joint

This is the strongest of the T-joints. Use it on heavy framing and in general furniture work.

The thickness of the tenon, which is cut on the rail, should not exceed one-third of the thickness of the upright or stile.

Select your chisel — a mortise chisel is best, but a firmer chisel will do — and set the mortise gauge points to its width. Centre the points on the edge of the work and mirk off the mortise and tenon. Cut the mortise, using either of the To make the joint, mark the width of the rail on the stile, and continue the lines all round the stile.

 

On the outer edge of the stile, mark lines for the wedges — about 3 mm. (1/8 in.) outside existing lines. Then square a shoulder line right round the rail to give a tenon length just greater than the stile width.

Then cut back to the wedge on the outer edge.

Saw down the tenon faces and cut carefully across at the shoulder lines.

Glue, assemble and cramp up, then hammer in the wedges. Smooth off the protruding tenon end and wedges when the glue has set.

Mortise and tenon variations

Variations of the mortise and tenon serve two main purposes: to strengthen the joint for a specific job, and to hide the construction.

The commonest variation is to cut extra shoulders, reducing the width of the tenon by 3-12 mm. (1/8 – 1/2 in.) top and bottom.

These shoulders completely hide the ends of the mortise slot and the tenon itself. Check with a try-square and trim with a shoulder plane for a perfect fit.

On double rebated work, like the central rail of a frame intended for panelling, cut the tenon back to the width of the rebate on each side.

Both these variations are glued and wedged as described for mortise and tenon joints, or dowelled as described below.

Haunched tenon

This is the strongest possible joint for window-frames, doors and furniture. It can be used as an L-joint — on corners — as well as a T-joint. The haunch can be sloping, instead of square as shown below.

The haunch resists twisting but does not over-weaken the stile, which the tenon would do if it were full width.

Proportions are important. Make the mortise and tenon about one-third the thickness of the wood — any wider, and the stile will be weakened.

Make the length of the haunch not more than one-third the length of the tenon. Its depth should be no more than a quarter of the width of the stile, or 12 mm (½ in.) — whichever is the smaller. Often the depth is determined by a groove in the frame.

Leave at least 12 mm. waste on the end of the stile, to prevent splitting during the making and fitting of the joint.

The waste should remain uncut for as long as possible after the glue has set. It protects the corner until final fitting.

Double tenon

Use a double tenon where a single tenon would be so wide that it would weaken the upright.

The joint has great resistance to twisting where extra-wide rails have to be fitted to uprights. Set it out and cut it as for the single tenon.

The number of tenons need not be limited to two. Use any number, equally spaced, on very wide work such as carcase construction.

Multiple tenons, neatly wedged and trimmed, give a satisfying appearance on functional designs. Use power tools wherever possible because of the amount of tenon-cutting involved.

Stub tenon

This joint serves much the same purpose as the plain mortise and tenon, but the tenon is stopped short so that it does not appear on the outside.

Use it where appearances count, or where the full strength of the through-tenon is not needed, as in fixing intermediate rails in doors and carcases.

The depth of the mortise should be about two-thirds the width of the wood. Cut the tenon about 3 mm (1/8 in.) short of this measurement to prevent it touching the bottom of the mortise.

Use dowels through the stile and the tenon to give extra strength to the joint.

Scribed tenon

The scribed tenon is used where the work has one or both edges moulded, such as on window-frames.

Mark and cut both shoulders of the tenon to the depth of the rebate. Then, with a scribing chisel, cut away a concave shape in one of the shoulders to match the moulding on the upright.

An alternative and slightly simpler method is mitring. Cut mitres on each moulding on the rail and a corresponding recess in the moulding on the stile.

Twin mortise and tenon

This joint is mainly used on the centre rail, or lock rail, of door-frames. The divided tenons span the lock, which is mortised in from the outside.

The gap between the tenons is at least 38 mm. (1-1/2 in.) wider than the lock so that the lock mortise will not seriously weaken the construction. There is a 12 mm deep haunch between the two tenons to give extra resistance against twisting.

The joint should be used on any rail wider than 150 mm (6 in.), even if no lock mortise is cut. A mortise the full width of the rail would seriously weaken the stile.

27. June 2011 by admin
Categories: Joints, Woodworking | Tags: , , | Comments Off on Woodworking: Housing Joints and Tenon Joints

Follow

Get every new post delivered to your Inbox

Join other followers: