Curved Dovetail Box


Curved Dovetail Box:
David Barron makes a lined box with curved ends.

David Barron makes a lined box with curved ends

Having made a box with angled dovetails, I decided to have a go at making one with curved dovetails. I’ve seen lots of boxes where the dovetails have been cut square and then the sides rounded; although  this is a simple method it leaves the dovetails much thicker at the middle as the baseline does not follow the curve of the sides. It does, however, give you square sides to the inside of the box, which is desirable for lining. So I decided to go for evenly curved dovetails while retaining square sides on the inside of the box.

Marking the tail boards
At this stage it’s best to mark everything clearly out on both ends of each tail board. I used one edge to run parallel lines to mark out the centre points of the tails as well as the waste areas on the top and bottom, indicated by the diagonal lines. A cardboard template was used to mark the curves, making sure that each of the pieces was marked the same distance in from the ends, ensuring square corners in the finished box. The dovetail spacing needs to be even to look good and this was easily achieved by making sure the parallel lines were evenly spaced. Having a pin in the middle of a set of dovetails is always my favoured option and this is even more visually important when used on a curve. While the board end is still square, a normal dovetail template can be used to mark out the tails in the space between the two curved lines.

The tail board marked up showing the waste areas

Adapting the cutting gauge
The first thing I needed to do was adapt my cutting gauge to cope with marking along a curved edge. This was done by reversing the head and filing a curve to the face that is greater than the curve I intended to use. This meant that there would be two points in contact with the curve as the marking was done. I have kept the gap between these two deliberately small (13mm) to keep material waste to a minimum (this will be explained later). Wheel marking gauges are not suitable for adapting and the best blade is one which comes to a point rather than the thumbnail profile of the gauge I used.
When using the adapted gauge it loses contact with one of the two points before reaching the edge of the board. So for this box with a finished height of 62mm, I cut all sides to 92mm to provide support for the gauge. The wider the gap between the two points on your gauge the more material you will need to add to your finished height. Although a little wasteful, this was the best of the various options I came up with.

My adapted cutting gauge to handle curves

Shaping the curve
Shaping the curve is easily done on a disc sander but I wanted to make sure that the corners to be joined were a perfect match for each other. So I assembled the box with double-sided tape using an accurately cut spacer block to make sure it was perfectly square. In this assembled state the curve can be cut on the bandsaw and refined on the disc sander, but you must make sure the table is perfectly square to the disc. Convex curves are easy to get smooth on a disc sander, especially if you use a finer abrasive. I used a 240 grit, which, although slower, was a lot more controllable and left a fine finish. The curved baselines can now be carefully marked on the tail board before disassembling the parts with a tail vice or spreader clamps. Please remember to mark all the parts before taking apart or this will result in lots of head scratching afterwards – trust me, I know! I applied my coloured dots at the beginning but had forgotten that they would be removed from the pin board as the curves were cut.

Sanding the convex curves on a disc sander

Marking out the baseline on the tail board

Assembling the box using double-sided tape and an accurate spacer block

Marking and cutting the dovetails
With the gauge on the same setting, the depth of the dovetail can also be marked on the end grain of the pin boards. I realised that the pin on the gauge had the bevel facing the wrong way for this cut but changing it round would have lost the setting, so I just made a lighter cut, knowing this would be planed out later anyway. It’s always a good idea to retain the setting on the gauge until the end of the job, so I used another gauge, set to the thickness of the tail board, for the final marks across the face grain of the curve.
Now it was time to cut the tails. I angled the boards to 1:6 so that the cuts on each side of the dovetails were made vertically, which I find helps with accuracy. The waste was removed with a fretsaw and then chiselled down to the base line. Although this line is curved, it is only 6mm wide so I just used a straight chisel to make the final cut.
I removed the waste on the bandsaw from both the tail and pin boards and planed them smooth on the shooting board. 

Marking out the end grain of the pins

Cutting the tails

Marking and cutting the pins
With the tails finished, the pins could be marked. The flat inside surface meant I could use my alignment board which kept things square and matched up the bottom edges of both boards. Once the pins were marked, they were cut all the way across and down to the gauge line. The fretsaw was used to remove the majority of the waste and I made sure I cut well into the back of the pin (which is in the waste) making removal back to the gauge line easier and less likely to split. This is very similar to removing the waste from the smaller pins of houndstooth dovetails (see ‘Houndstooth Dovetails’ video on YouTube:

Marking the pins using my alignment board

The finished tail boards

Saw cuts made on the pin board

The finished pin board

Routing the grooves
The groove for the 4mm ply base was then cut on the router table using the same bottom edge, as on the alignment board, against the fence to ensure the grooves lined up perfectly. The top of the inside surfaces were smoothed and finished and the box was glued up, making sure all was square. The ends were rounded smooth on the disc sander with 240 grit and the sides were cleaned up with a sharp plane and sanded to a fine finish. The second base was stuck to the plywood one, adding weight as well as giving a lift to the box. Homemade leather bumpers were also added.

Cutting the grooves on the router table

Cleaning up the sides including removing all trace of the base lines

The lining being shot on a mitre shooting board

Additional base stuck in place

Homemade leather bumpers being made

Finishing touches
The base inside was lined with padded pig suede and the mitred linings were planed on the shooting board to a tight fit. As I had chosen a highly figured piece of amboyna (Pterocarpus spp.) for the lid I decided to make it a tilt top rather than add a handle. This was simply achieved by lowering one end of the lining and angling the two sides to match. The lid can be tilted down with a finger and removed with the same hand.
The whole box was sanded carefully down to 320 grit followed by four coats of melamine laquer. After allowing an hour to harden this was cut back with 400 grit Abranet followed by 600, 1000 and 2000 grit Abralon pads to leave a silky matt sheen.

The angled lining in place

The action of the tilt top lid


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