The variations in dovetail joints do use some of the basic principles of the through dovetail.
The three types of dovetail joint mentioned here should only be used with hardwood and on “1: shape or carcase-type constructions.
The effect of this type of joint is to conceal it from the front view and help prevent it moving out of square, both of which are particularly important in drawer construction. The lap feature is essentially a rebate and comprises not more than one third — and not less than one sixth — the thickness of the timber in which it is formed.
When marking out, remember the side of the construction with the tails in will still show when the joint is made; the hidden parts of the joint are in the other piece, which should be the thicker piece if you are joining timber of different thicknesses.
As with the through dovetail joint, the tails are made first and should be marked out to not less than two-thirds the thickness of the other piece of timber — and not more than five-sixths. They are then cut out in the usual way.
When marking out the other piece, score the depth line with a sharp cutting knife across the inside face of the timber. The depth line should be the same distance from the end of the timber as the length of the tails.
Hold the tails in position over the end of the piece of timber in which the pins are to be cut and score around them with a sharp cutting knife. Shade in the waste wood at this stage to save confusion. Square down from the marked lines to the depth line on the inside face. With a dovetail or tenon saw, carefully cut the sides of the pins diagonally until the sawcut reaches from the depth line at one end to the bottom of the pin recess at the other.
Always cut to the waste side of the wood. Remove the remaining waste carefully with a sharp bevel edge chisel.
To ensure a straight joint line on the inside face when chiselling out the waste, clamp a square piece of scrap wood against the depth line to act as a guide for the chisel. This helps to ensure a square, flat-bottomed recess. Take care not to cut the recess too large or the joint will be weakened.
Double lapped dovetail This joint demands particular accuracy since there is no allowance for error. It is a very strong joint and leaves only a small amount of end grain exposed; but it should only be made with pieces of timber of the same thickness. First cut out a rebate in the pieces of timber which will form the front and back (or top and bottom) of your construction. The rebate should be marked out to a depth of not less than two-thirds (and not more than five-sixths) the thickness of the timber and a width of not more than one-third (and not less than one-sixth) the thickness of the timber.
The recesses are cut on the inside faces of the timber; mark out the depth line for the recesses, which should be the same distance from the end of the timber as the thickness of the timber. These pieces of timber will be used for cutting out the pins and, contrary to previous dovetail joints, these are marked and cut out first. Mark out the pins on the sawn surface of the rebate. When chiselling out the waste, use the scrap wood guide as before.
When you have cut out the pins, hold the piece in which the tails are to be cut in position in the rebate and mark round the pins, preferably with a sharp veneer cutting knife. Again shade in the waste wood.
Mark the depth line on the piece of timber in which the tails will be cut from the piece in which the pins have been formed (equal to the width of the rebate). Cut out the tails with a sharp bevel edge chisel as before.
Dovetail joints can be used to form a “T” joint in a frame structure. When forming joints in the timbers face-to-face, a dovetailed halving joint is used. When joining the timbers end-to-face, the through or stopped dovetail joint is used. You can simplify the joints by cutting the dovetail angle on one side only; these are known as barefaced dovetail joints.
Dovetailed halving joints
You can use this joint to join timbers of different thicknesses, provided the tail is cut in the thinner timber which forms the stem of the ‘T.
To mark out the joint, score the depth line with a sharp cutting knife all round the timber in which the tail is to be cut. This line should be marked from the end of the tail piece 2mm more than the width of the timber in which the pin is to be cut; the 2mm allowance can be trimmed off when the joint is formed.
Set a marking gauge to half the thickness of the timber in which the tail is to be cut, place the stock against the front face of the timber and score across the end of the timber and down both edges as far as the depth line.
With the gauge at the same setting, hold the stock against the front face of the timber in which the pin is to be cut and score along the top and bottom edges of the timber.
The width of the half-recesses on each side of the tail should be one sixth the length of the tail at the depth line. Mark the half-recesses on the front face of the timber in which the tail is to be cut. Join these marks by scoring with a knife to the outside edges of the tail at the end of the timber; this automatically gives the correct dovetail angle.
Cut the halving joint in the same timber.
Cut out the tail with a tenon or dovetail saw, making sure you keep to the waste side of the cutting lines. Rub the tail smooth with medium fine, then fine, glasspaper and position it on the front face of the other piece of timber; score carefully round it with a sharp cutting knife. Mark the waste wood and, with a knife and try square, continue the pin lines down both edges as far as the depth line already marked. Carefully saw down to the depth line, keeping to the waste side of the cutting lines, and remove the waste with a bevel edge chisel. Clean up the bottom of the recess with a router.
To make a barefaced joint, omit the dovetail angle on one side of the timber in which the tail is cut.
When glued and clamped, the joint may be additionally strengthened by the use of pins or screws.
Single through dovetail This joint is used when fixing timbers end-to-face to form a ‘T. The pieces of timber must be the same width, but the stem of the “T.’ can be thinner.
First mark out the tail; its length must not be more than one third or less than one half the thickness of the timber in which the pin is to be cut.
The joint is formed in the same way as for the normal through dovetail, except the waste wood must be removed from the pin recess with a bevel edge chisel and the bottom of the recess finished off with a router.
Single stopped dovetail This joint is made in a similar way to the through dovetail, except the pin recess is not cut right through the timber and the tail is cut shorter to fit. This gives the appearance of a butt joint. The waste wood in the pin recess has to be removed almost entirely with a bevel edge chisel and so the joint is a difficult one to make accurately.
The length of the stop (or the amount of tail to be cut off) is normally the same as the thickness of the tail piece timber.
Single stopped barefaced diminished dovetail
This joint is used for shelves in cabinets, where the shelf helps to hold the sides of the cabinet together. The barefaced side usually forms the top of the shelf and the tail tapers from back to front on the shelf; this makes it easier to insert the shelf from back to front and ensures a close fit for the barefaced side of the joint.
Warning This joint is one of the most difficult of the dovetails to make and requires a great deal of skill and patience. Always practise on scrap pieces of wood before starting the work.