Joints

JOINTS

Butt joints

Butt joints are the easiest of all to make. Wood is butted face to edge or end to edge and nailed, screwed or dowelled together. End to edge joints can be joined with corrugated fasteners.

Strength can be added by glueing the joining faces. These joints are not recommended for hardwood unless pilot holes and screws or dowels are used to hold them together.

When nailing or srewing but joints use corner or mitre clamps to hold the two pieces in place.



End to edge butt joint.



Halved joints or lap joints are mostly used to assemble light frames which are going to be covered with hardboard or plywood. Half the thickness of each piece of wood to be joined is cut away with a tenon saw and the joint is glued and screwed or nailed. Halved lap joints are also used to join long lengths of timber as for fencing.

Tee half joint



Mitre joints are always cut to 45° in a mitre box so that they will form a 90° corner when joined. As no end wood is ever seen these are very neat joints but they are weak. Normally used for picture frames where they are nailed with panel pins. When used for other purposes they must be strengthened with glue blocks, angle braces or loose tongues. Mitre joints should always be glued.

Mitre joints

Lap or halved joints

When nailing a mitre joint always start the nail with one part of the mitre above the other. The nails will pull the mitre into square.






Rebate joints are suitable for joining top and bottom ends of furniture. Stopped rebate joints hide the joint. Glue and skew nail, or screw the joint together.



Stopped rebate joint


Housed joints are mostly used for shelves. The stopped house joint hides the actual joining. Use skew nails or screws to fasten the boards together.



Stopped housed joint



Loose tongued joints are used to join planks edge to edge to form a larger board like a table top in which case they are always glued only.


Bare faced tongue and groove or Loose tongue and groove joints can be used to join chair rails to chair legs. Note the glue blocks for extra strength.





Tenon and mortise joints are very strong joints mostly used in furniture making and for heavy doors and gates. They are not easy joints to make. The secret in making a good tenon joint lies in careful and accurate marking.The tenon’s width should not be less than a third of the thickness of the wood especially if wood of the same thickness is joined. The shoulders may be of any width and may also be offset when the mortise is made in rebated wood. Make the mortise before rebating the wood. If the top of the mortised wood is to be in line with the edge of the tenoned wood a haunched tenon can be made with the haunch cut back to be in line with the shoulders.

Haunched tenon joint











Beveled haunched tenon











Marking and making mortise and tenon joints.

1. Mark the depth of the tenon on both edges and faces of one of the pieces of wood.
   
2. Set the pins of the mortise gauge to the width of the tenon and set the block to the width of one shoulder. Mark the tenon on the edges and end of the wood.
   
3. Using the same settings of the mortise gauge mark the mortise on one side of the other piece of wood.
   
4. Set the marking gauge to the centre of the mortise and mark a centre line.
   
5. When making a blind tenon drill holes (with a diameter slightly smaller than the width of the tenon) closely together along the centre line at a depth slightly more than the length of the tenon to create an escape route for excess air and glue. A 1 mm (or smaller) hole can be drilled from the side into the base of the mortise for the same purpose. This hole can easily and unobtrusively be filled with wood filler or beeswax if necessary. When making a through tenon it is best to mark the tenon on both sides of the wood and to drill from both sides or to watch and “back drill” to avoid splintering the wood.
   
6. Remove excess wood with a sharp chisel, always working from the centre to the edges of the mortise. Keep edges of the tenon and mortise as sharp as possible.
   
7. Place the wood from which the tenon has to be cut at a 45° angle in a vice and with a tenon saw start cutting the tenon cheeks at the highest point on the waste side of the marking. When the depth line of the tenon is reached, turn the wood around and finish cutting from the other side. Then cut the shoulders and lastly the haunch. Remove excess wood with a sharp chisel till the tenon fits tightly in the mortise.
   
8. Glue the two parts together.
   
9. A dowel or screw inserted from the side may be used to strengthen the join.
   
10. A through mortise can be strengthened by inserting small wedges in the opposite end of the wood to hold the tenon in place.

Marking a mortise









Bridle joints or open mortise and tenon joints are used in furniture making especially to join the legs to the cross pieces. Marked in the same way as mortise and tenon joints the only difference is that the mortise is cut into the wood from the end.



Dovetail joints are very strong and neat joints used primarily to make drawers and boxes. It needs a lot of practice to make a good dovetail joint.














Marking for dovetail joints.

1. Square the ends of the wood to be dovetailed.
   
2. Set the sliding bevel to a suitable pitch of between 1 in 6 for heavy work and 1 in 8 for smaller and more detailed work. Avoid sharp angles as the points of tails break easily.
   
3. Scribe the tails on the end and face of the wood and mark the “waste” pieces.
   
4. Clamp the wood in a vice and cut on the waste side with a tenon saw.
   
5. Lay the two pieces over each other and transfer the markings through the cuts with a tenon saw.
   
6. Remove the waste between tails and pins with a chisel.

Lapped dovetails are mostly used for drawer fronts as they give a very neat, strong joint with only one side showing end wood. Marking is the same as for open dovetails but the cutting out between the pins needs a fair amount of chiseling. Special dovetailing bits are available for routers, which are ideal for this job.

Running dovetails

A very nice joint to use for fixing drawer sides to fronts but don't attempt it without a router.





Dowels are mostly used to strengthen butt, mitre and rebated joints but are also used to join wood when making or repairing small tables, chairs and doors. When joining wood to be rebated or grooved, drill the holes for dowels first. The diameter of a dowel should not be more than a third of the width of the narrowest wood to be joined. Cut the necessary length from dowel sticks and lightly chamfer the ends. Good dowel sticks have a “V” groove along the length to allow excess glue and air to escape. If your dowels do not have this groove you can run one in by using a marking or mortise gauge. Alternatively you can allow a little space at the end of the hole in which the dowel is inserted to allow for the extra glue and air but this will weaken the joint.

When using dowels to join cross pieces to small legs, stagger the dowels for maximum length and strength.

Glue blocks.
Small pieces of quadrant or a length of quadrant run the entire length of the joint make excellent glue blocks and give a neat finish especially on the inside of drawers and boxes.



Angle braces are always glued and screwed or nailed

Strengthening joints

Dovetail joints

Tenon and mortise joints

Tongue and groove joints

Housed joints

Rebate joints