Housing joints (dadoes) are used for fitting shelves and dividers in cabinets of solid timber or sheet materials. A housing is a precisely cut groove that accepts another piece of timber, usually across the grain. Structural quality is limited and it depends on a tight fit for rigidity. A dovetail housing is hardest to make, but is far sturdier, as it has mechanical strength. Either housing can be stopped so the end of the groove is not visible.
Tools you need
- 2H pencil
- Steel rule
- Try square
- Marking gauge
- Marking knife
- Bevel-edge chisel
- Tenon saw
- Paring chisel
- Router plane (not essential)
- Smoothing plane
- Sliding bevel (for dovetail housing)
How to make a thicknessh housing joint
1. Carefully mark the position of the housing by holding the shelf component (B) on the work piece (A) and pencil in the waste. The width of the housing should be a fraction less than the shelf. Square the two lines across the face with the try square and continue them around both edges.
2. Set the depth of the housing on the marking or cutting gauge. This should be about one-third of the thickness of the timber – deep enough to make a strong joint but not too deep to weaken the surrounding wood. Scribe the line along both edges of the housing. Holding the try square tightly against the work piece, scribe both lines with a marking knife. Make several shallow strokes rather than one deep cut, to a depth of about 2 mm (X6 in).
3. Cramp the work piece to the bench top before sawing. To provide a guide for the saw blade, open up the scribed lines to a ‘V’, using the chisel. Hold the chisel at about 45 degrees to the work on the inside of the housing, parallel to the line. Make a series of cuts pushing down into the incision, the blade edge 2 mm (1/16 in) inside the line. Do not use a mallet, which could make the cuts too deep.
4. Open up the ‘V’ by working along each line, with chisel-width steps. When one side is finished, turn the work around, if necessary, and repeat along the other side. The teeth of the saw blade should just sit against the side of the incised line. Start sawing with the handle raised slightly. While cutting, gradually lower the handle until the saw is horizontal. Stop cutting when the teeth reach the gauged lines at the bottom of the housing. During sawing, check the lines on the joint edges to make sure the cut is vertical.
5. Use the chisel and mallet to remove most of the waste. With the blade pointing up slightly, make a series of shallow cuts until you reach the gauged depth mark. Work in from each side, turning the work piece around when necessary. Both ends of the housing should now be at the correct depth, with a shallow, inverted V of waste remaining in the centre. On a board up to about 178 mm (7 in) wide, you can remove this with a long chisel held horizontally. Pare the waste down with shallow cuts until the bottom of the housing is flat. Check this with a steel rule held on edge. On a wider board, use a paring chisel or router plane to clean out the housing.
6. Check the fit of the joint and do any final trimming on the matching shelf (B). The end of this must be planed square. If the joint is too tight, carefully skim either face of the shelf with a finely set smoothing plane. Check constantly until the joint is a firm push fit. Depending on the overall length of the joint, select a suitable cramp for assembling. A bookcase will probably need a couple of sash cramps, while a G-cramp may be sufficient for a shorter joint. Use scrap wood to prevent the timber surface getting dented when you tighten the cramps. Apply glue to both pieces and check the joint is true with the try square. When the glue has dried, clean up the joint edges with a smoothing plane.
A housing is an ideal joint for the router. Hold similar panels together with a sash cramp and temporarily cramp a batten across them at 90 degrees. The batten acts as a guide for the base of the router, which should be fitted with a straight cutter. Adjust the batten to match the housing width. You can also machine a groove accurately with a radial arm saw or sliding mitre saw.
Stopped housing joint
Instead of running the groove right across the timber, it is stopped about 10 or 12 mm (3/8-½ in) back from the front edge. The end of the shelf is notched out to match the housing by the same amount. Alternatively, the shelf may be set back from the edge of the side panel.
How to make a stopped housing joint
1. Mark out in a similar way to a through housing (see page 204). Measure back the distance of the stopped part from the front edge of the work piece and gauge a line across the end of the housing. Using a chisel and mallet, chop out the waste material to form the end of the groove, removing a small amount at a time. The depth should be one-third of the board thickness. This cutout means you will be able to saw the housing from the rear edge.
2. Having scribed the outer lines of the housing with a marking knife, cut ‘V’ grooves with the chisel to guide the saw blade, as you did with the through housing joint. Remove the waste with the chisel and mallet, taking care not to damage the edges. Saw the sides of the housing and chisel out the waste carefully. Check the bottom is flat with a steel rule, and trim as necessary.
3. Mark the notch on the end of the shelf with the marking gauge. Continue the lines on both faces and the front edge. With the shelf held upright in the vice, remove the waste with the tenon saw. Check the shelf and housing fit together and make any adjustments carefully as needed.
Dovetail Housing Joint
Making a dovetail housing joint with hand tools is more challenging than a through housing. Although it is easiest using a router fitted with a suitable dovetail cutter, the hand-cutting technique provides good practice at controlling a chisel and tenon saw. Either one, or both, sides of the housing may be dovetailed.
How to make a dovetail housing joint
1. Adjust the marking gauge to one-third the thickness of the vertical panel and scribe a line underneath the end of the shelf. Continue this shoulder line around both edges and mark each one 3 mm (1/8 in) in from the lower face.
2. Set the blade of a sliding bevel from this mark across to the outer corner of the shelf. This is the dovetail angle and should be drawn on both edges. Scribe the line with the marking knife and saw across the shoulder line until you reach the dovetail slope.
3. Pare away the waste from the shelf with a wide chisel. A bevelled guide block will help keep the chisel at the correct angle. You can make this from an offcut and simply move it along the end of the timber as you pare the dovetail.
4. Carefully mark in pencil the location of the dovetail housing on the side panel, squaring the lines around both edges. Then transfer the depth of the housing with the marking gauge. Using the sliding bevel, mark the dovetail slope on both edges, checking that it is the correct way round with the profile of the shelf. With the blade tilted for the lower line, saw along the sides of the housing until you reach the bottom. Again, an angled block is useful here to guide the saw. With a bevel-edge chisel, cut away the waste and clean up with a router plane.
Word Discription :
Dado A wide, shallow groove across the grain. Alternative name for housing.
Paring Removing a thin shaving from timber with a sharp chisel, either from the surface or from end grain.