Before we can proceed to shape the carcass, the mechanisms must be completely installed and operating properly. With the mechanisms in place, the challenge becomes mounting the main box and tabletop to them. The tabletop is relatively straightforward: center it on the carcass, then mark the top racks. The main box, however, isn’t so simple. Not only does it have to be located left/right, front/back within its opening, but it also needs to be situated in height above the carcass floor. If it’s too high, the bolt on the latch won’t catch; too low, and the bolt will drag on the main box as it opens. To complicate matters, it is impossible to directly mark any of these components. They’re buried deep in the carcass interior!
Being the case, I’ve devised the following plan…
- With the tabletop removed, center the main box between the lower racks in the carcass. This dictates the thickness of the shims that will be needed.
- Remove the top racks such that the main box can be lifted out versus slid through the front.
- Coat the latch bolt with graphite.
- Retract the latch bolt by turning the key, and place the main box into the carcass. Align it appropriately, then release the latch bolt. This should imprint a line on the underside of the main box where the latch makes contact.
- Align the back of the hole in the metal latch plate with this line.
While I’m certain some level of adjustment will be necessary, this methodology provides a plan to move forward. Such is the nature of product development or, to put it another way, if we knew what we were doing, it wouldn’t be called research!
The main box latch is the trigger for the table’s entire mechanical system. When the key is turned within the right side apron, it actuates a lever releasing a bolt from the bottom of the main box. Under the tension from the drive mechanisms, the main box is propelled forward while, simultaneously, the table top slides back. Before proceeding with the mechanisms, it’s necessary to mortise in the main box latch.
This is a bit of a delicate operation. The latch mechanism has a 90° bend where the key connects which has to be mortised behind the lower rack guide. It also has a sleeve into which the key is inserted. This needs to be contained within the apron, not protruding from it.
After a bit of drilling, sawing, and paring things finally slide neatly into place!
Next, the long portion of the mechanism must be mortised into the floor of the carcass.
Up to this point, we’ve seen the top racks and the drive mechanisms installed in the side aprons. The final pieces to address are the lower racks. While the tabletop attaches to and rides on the top racks, the lower racks mount and support the main box. Like the upper racks, the lower racks engage the drive mechanisms and span not only the apron, but also both legs. So, we need to be careful about their alignment. An additional complication is that the rear end of the lower guide is blind mortised into the rear leg, while the front end is grooved. The main box is supposed to be removed through this groove for assembly and maintenance. To hide them, the grooves get covered with dovetailed keys veneered to match the rest of the carcass, then covered with guilt bronze mounts. No one will ever know…
While making the prototype, I’ve had to keep the aprons rough to facilitate installation of the mechanisms. No sense in making them curvy when I’ll need to stabilize them for mortising. This week, however, the project is starting to turn a corner.
To install the lower racks, there need to be defined boundaries. Unlike the upper racks which extend beyond the carcass, the lower racks are contained within the carcass, and are unseen. This means knowing the extents of aprons once they’re shaped. I created a template from photos of the original, and referenced it from the center line on each side block. Repeat the process on the undersides. These lines can now be carried down the verticals on each leg for reference during final shaping.
I recently received an e-mail from Joe, a Kickstarter backer, inquiring about the progress of the marquetry rewards. Looking back, I realized that this was the last time I posted on this topic. Much too long without an update!
As discussed in that post, the red box in the figure shown below highlights the section I’m considering for the marquetry projects. I’m editing it to remove extraneous pieces that won’t make sense in that context, but it will include two flowers and a good portion of the ribbon binding the stems.
I used a modified double bevel technique for convenience. That is, the saw is held at a slight angle with respect to a line perpendicular to the surface of the veneer. This allows the top piece to perfectly conform to the bottom one when the waste is removed. No gaps! Veneer is cut two pieces at a time, each cut adding a new element. Slowly, the artwork takes shape.
Early stage marqutery prototype
Sometimes the pieces can become quite small and fragile. With this method, they don’t remain that way for long. They are quickly attached to the assemblage becoming part of the whole. The following image of the upper flower in-process provides a measure of scale.
Scale of the flower
As each flower is completed, it is cut into the background and the picture emerges. Once the piece has been mounted to its core, we’re looking at the back (glue) side in the image below, the binding paper is removed and a sealer applied. The lower flower can then be “engraved” and the resulting lines filled to add detail. There is still plenty of work to be done before this piece is “finished”.
Based on my current schedule, I plan to begin working on the backer marquetry as soon as the prototype is finished. Probably, this summer. The idea is that by working the marquetry all at once I will become conditioned to its intricacies, my efficiency will increase, and this will put me in good shape to create the final piece for the tabletop.