Tambour Traveling Desk
Boston c. 1800
by Robert L. Millard

  In this article I will describe the construction of a unique portable desk, based on examples attributed to the shop of John & Thomas Seymour. Apparently there are 10 desks of this configuration, still surviving.  I was able to find photos of five of the originals. All the desks display a decided Regency influence and the tambour section, reminds me of a Roman fasces.
  Like all small projects this desk requires careful workmanship, because it will picked up and examined closely. Also, considerable precision is required if the tambour is to operate smoothly, close properly and fit well.

Design

  The tambouur is attached to the drawer, so as the drawer is opened, the tambour is also opened, revealing the tray section. A careful look at the photos of the originals showed that when the tambour is open to the point where is lies in flush with the top of the tray section,  the drawer protrudes enough that it supports the writing surface in such a away that the writing surface lies in one plane. When closed the tambour holds the writing flap in place and the drawer is flush in its opening. Getting all these factors to come together correctly required a full size cross-section drawing. The only description I could find of the construction of the original was in The Mussey book and it was rather cryptic, so I applied my own interpretation of the construction details. I would much rather have specific construction details to go by, but period craftsmen would have seen pieces in design and price books and applied their own joinery methods, much like I have done here. 

Making the case

  The case sides and back are made from ½” thick solid mahogany. The back is beveled on its top inner edge to provide clearance for the tambour. The miters joining the sides to back are reinforced with splines that stop short of going through the top edge. The turrets are turned on the lathe from 5/8” thick stock, glued to a sacrificial block mounted on the face plate. Saw and plane away the mounting block and using a centering head, find the center on the inside face of the turrets; this center will be used later, when routing the groove for the tambour track.

  The turrets are rabbeted where they join the sides. I did this with a chisel and a small scoring saw. This is a delicate task, because the lip is quite thin.

Chiseling rabbet on the turret

The scoring saw was used to make a kerf on the circumference, and the chisel cleared away the waste. The sides have an arc cut in them to correspond to that of the turrets. These cuts have to be precise, so that when the turrets are glued in place, both the right and left sides will mirror each other perfectly; failing to do this will result in the tambour not tracking or closing properly. The turrets are joined to the sides with a butterfly key; locate the key so as to keep the center point previously marked on the turret. This butterfly key detail is one of several areas where I applied my own construction method, in the absences of hard information about how the original was constructed. When gluing the turret in place it is critical that it be perfectly flush and true with the inside face of the side; if it were not the tambour would bind or have an imprecise fit (i.e. if the turrets leaned in or out, it would be impossible to get a precise fit on the tambour).

The track for the tambour is routed with a 3/16” router bit and a guide collar, against a template, to a depth of 3/16”. The track of course runs concentric with the turrets. At the point where the turret intersects the back, the track then runs tangent to the turret  at a 60 degree angle, before turning to the horizontal plane, at the level of the groove in the drawer bottom. Make the track template, taking into account the offset (I always have a hard time with this). Since this template will reflect the finished track, the layout and cutting must be carefully done, to insure a properly fitting and smooth running tambour.  

click for larger image

Drill a ¼” hole at the center of the circular portion of the template; this will be used to locate the template over the side using the marked center on the turret. Tack the template in place and route. The groove stops short of the front by about ¾” and is stopped at the level of the fixed writing surface. A supplementary groove is chiseled by hand to permit the insertion of the tambour into the glued case.

This groove is located about 1 ¾” from the front and is generously sized, since the tambour will need to be bent, opposite of its normal direction, where is it is less flexible. Also, the groove won’t show in the finished piece, so little care needs to be taken in chiseling it.

  The fixed writing surface is made with a pine core of narrow boards glue together in quarter-sawn fashion, then cross banded with veneer, and finished with a layer of pine face veneer: in effect this makes a piece of lumber core plywood, which will remain stable (see page 3 of this article for more information on veneering). This stability is important because of several issues, one side of each leaf will be covered in baize and will pick up and give off moisture at different rates, and there are significant cross grain issues; even a slight amount of warping will prevent the leaves from closing properly and this would effect the fit of the tambour. The fixed leaf is attached to the sides with a spline joint, and is later reinforced with glue blocks. The writing surface is offset below sides by the thickness of the baize. The case can now be glued together; I used hot hide glue with a urea additive to extend the gel time.  After the glue has cured a rabbet is run on the bottom of the case that will house the bottom board; this rabbet stops short of the front by the thickness of the drawer front, (the bottom board acts as the drawer stop, so this stopped portion must be cut accurately) and is done on the router table with piloted bit. You’ll have to clean up the corners with a chisel.

  The hinged leaf is constructed in a manner similar to the fixed leaf, but has a few differences. The core is sized so its final thickness after cross banding and face veneering is the thickness of the baize less than ½”. After cross banding, but before face veneering, a strip of solid mahogany is glue on to the side opposite the hinged side (here after called the free side) and planed flush with the surfaces; this is done so that the pine core does not show on the finished leaf when in the open position. The face of the leaf is veneered with a highly figured piece of mahogany crotch veneer, and the inside face is veneered with pine. (See the veneering page for information)  After the veneer has dried the top is trimmed to the exact size, noting that the hinged edge is beveled to match the slope of the writing surface. A ¼” deep by 3/8” wide stopped groove is run on each end. Into this groove is glued a strip of wood, to provide a face grain to face grain glue joint with the solid mahogany edging. The ends and hinged edge are trimmed with solid ¼”x ½” mahogany strips mitered at the corners. These are compound miters due to the beveled hinge edge. To ease the installation of these edging pieces I made them slightly over-sized for width and later planed them flush.
   A strip of mahogany veneer the thickness of the baize is glue on the inside face to the free side and ends, forming a frame for the baize. To minimize the impact of the joint between these strips and the solid edging, I routed the solid strip leaving just a 3/64” lip. This was done with a router, and a piece of the edging veneer taped to the router base, to control the depth of cut. Some very careful chisel work was required to clean up the edges and corners of this router cut. From the photos of the original, it is apparent that this was how they were done (well, certainly not with a router, but the end results were the same). A ½” wide piece of the same thickness veneer is glued at the joint between the fixed leaf and the implement tray, after the tray has been fixed in place (more on this later). 

The Drawer and Implement Tray

  The tray section is made from 3/16" mahogany, with half blind Dovetails joining the corners. The dividers are let into stopped dados. Small triangular blocks support the lids. The bottom is sized to fit inside the sides and glued in place. In order to have the tray as large as possible, a bevel has to be planed on its rear bottom edge to provide clearance for the tambour.  Dry fit the tray in place, taking care that the tray is level across the front, parallel to the back, and allows room for the tambour to run. With the tray just clamped in place, now you can fit the strip of veneer that forms the frame for the baize. With the tray, and the boarder around the baize finished and rubbed out, you can secure the tray in place with small glue blocks. 
  The lids are pieces of solid birdseye maple ¼” thick with turned decorative depressions surrounding turned rosewood knobs. The lids are cut slightly over size for width and length and glued to a sacrificial block and mounted on the face plate. Extra caution is required when turning the long lids, as it is all too easy to not see the edges at the circumference while spinning. The center of depression is turned to receive a tenon on the knob. After the sacrificial block is removed the lid is planed to fit its opening, taking care to keep the depression centered.  The knobs were turned, taking care to have them appear identical, and finished on lathe with padding lacquer.
  The drawer is pretty standard construction, being joined with half blind dovetails at the front, through dovetails at the rear, and grooved to receive the bottom. The only deviation from standard is that the sides are ½” narrower than the front, so that the drawer front can conceal the case bottom. Also, since the drawer bottom serves as the attachment point for the tambour, it is glued to the drawer back. So that the drawer bottom is free to expand, I cut the groove in the front deeper than normal, and left the bottom loose in the groove, here. The sides and back are made from 3/16” cherry, and the front from 5/8 Mahogany; the front is this thick in order to accommodate the lock and allows for long, fine pins on the dovetails which look nice.