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Sliding Dovetails

The current challenge is to cut sliding dovetails to the sides of a curved carcase. Ordinarily, this would not be too complicated if the dovetailing was completed from the rear and the front faces. However, since the chest sides are frame-and-panel, I wanted to form the dovetail housings for the front drawer blades from inside the legs. To do this I came up with a strategy to add a fillet to the rear and make the rear and front housings in one section.

We left off last weekend with the fillets marked to position the 18mm thick drawer blades. These lines represent the lower edge of the drawer blade.

Below are the boards for the drawer blades, which are ready to be cut to length. These are all double-width as, once completed, they will be ripped into two equal sections for the front and rear of the chest.

Similarly, the fillets at each side of the carcase will be divided and added to the front and rear of the chest. This will ensure that the front and the rear housings for the sliding dovetails will match exactly. The front section of the fillet will provide a template to extend the housing into the front legs.

A straight edge is clamped to each side of the carcase, at the line shown above.

An adjustable pinch rod is used to measure the exact internal width (leg-to-leg).

This is transferred to the drawer blade board. An extra 12mm is added to the total length for the 6mm dovetail at each end that will house in the leg. The board is sawn to length and squared on a shooting board.

Above – the 6mm wide line for the dovetail.

A rebate 6mm x 12mm is sawn.

Some may be aware that several years ago I built a plane for sliding dovetails. This cut the male section. More recently I built a plane to cut the female housing.

A while back I began thinking of a simpler plane that could do both male and female joints. In part this was inspired by Terry Gordon converting one of his side rebate planes to cut sliding dovetails.

The weapon of choice for me was the Stanley #79, a double-ended side rebate plane. I liked this as it has a long depth stop and body, both which would provide more registration area than a singe-ended rebate plane.

The only modification needed was to add a wedge under the depth stop to alter the cutting angle from 90 degrees to (my preference) 1:7 – this is the same as the other planes I built, and works well with the hardwoods I use.

Set the lower edge depth stop flush against the edge of the board. This tilts the plane at the correct angle. Set the blade for a fine shaving. This is a low cutting angle and will pare away the wood quite quickly. The tip of the blade is left pointed and extends slightly below the body. This works in the same way as the blade of a rebate plane extended a fraction beyond the body to ensure that the corner is removed.

Note that this plane does not stop cutting when it reaches the desired depth (as the original dovetail plane does). An alternate method is described below.

First step is to scribble a contrasting colour on the surface to be removed. This makes it easier to see where- or where not the cut has been made.

Above: the yellow shows that there is a smidgeon at the edge left to be removed.

Once the drawer blade has been dovetailed, it is returned to the supports at the lines for marking.

I find that it is easier to use a sharp scratch awl to transfer the outline of the dovetail to the legs (Tip: sharpen the awl on a fine deburring wheel).

Above: The transferred dovetail along with the outer lines of the housing. The line to the left represents the baseline of the drawer blade.

Note that the dovetail is angled. This occurs to a greater- or lesser degree depending on the amount of curve involved.

I chose to use a duzuki to saw the sides of the housing as it enables the sawing action to avoid striking the center panel reinforcement. The sliding bevel was helpful in checking the slope.

Because the floor of the housing is angled, a router plane cannot be used for smoothing and leveling. This is not a problem since the housing is short (100mm/4”). It is important to check the level with a depth gauge. Set this on the face end first …

and then transfer this to the far end. Chamfer the end, both to avoid spelching while chiseling out the waste, as well as a visual guide to the amount of waste to be removed.

Now you can zip the waste out with a paring chisel …

checking the depth and level as you go.

Clean up the sloped side with the dovetail plane.

Where the sides of the carcase curved more, it was necessary to shape the housing to fit the dovetail. A small shoulder plane was used to chamfer the edge ..

So far the fit has been great. What is reassuring is that the strategy to fit the front sliding dovetails from the rear looks like it will work.

Below: The rear of the carcase, with the housing stretching across the rear legs and fillet. The fit is tight and there are no gaps to be seen.

Progress to date: four drawer blades completed. Three to go - the lower, eighth drawer, does not require a sliding dovetail as the drawer blades can rest directly on top of the bases.

Once these are completed, the fillets and the drawer blades will be ripped and attached front and rear. The front legs are still to have the housings cut, and the drawer blades still require the bow to be added to their fronts for the bowed drawers.

Regards from Perth


July 2015