I had thought at one point, or should I say, my wife suggested, that a good title for this thread would have been “The Bonfire of the Vanity”, however, things didn’t go quite that far south. No need for incineration thankfully, though it did cross my mind that December.
Last time, I detailed the construction of the frame and panel top. Now I’ll go through the steps I took in attaching the top. While a quick method to do that might have been screwing it to the cap rail from underneath, the problem with that is it does not allow for the pieces to move independently of one another, to allow for seasonal movement in other words. This can be overcome by using elongated screw slots, and perhaps machine screws in brass screw cups, but I chose to use an all-wooden joinery connection that allowed for a solid connection that was also lockable and demountable. This connection is known as ‘secret fixing’ or ‘concealed keyed sliding dovetail’ in the West, and involves making small double-dovetail shaped keys. These keys are known in Japanese as sui-tsuki ari (吸い付き蟻).
These keys find use in high-class work in Japanese wooden architecture, for providing concealed connection between veranda floorboards and the supporting framework, among other applications. Often, the pieces to be fixed are superimposed upon each other and these keys are driven in to fix the assembly. In the case to be described here, I chose to attach the keys to the top, semi-permanently, and then the top would be offered up as a unit, dropped into place into the cap rail mortises, slid back to lock, and then tapered keeper pins would secure the connection from coming apart.
I used Gabon Ebony for the keys, and cut them out on the tablesaw. Making the keys is comparatively easy. Once I had the them prepared, I set to work on the cap rail mortises. Both cap rail and the top frame rails would receive the mortises, but the top’s mortises would receive the semi-permanent dovetail keys.
Here’s a picture of a completed mortise in the cap rail:
Then I processed the mortises in the top. The keys are dropped into the open end of the mortise and tapped back into the enclosure :
Here’s the key dropped into place and ready to be tapped home:
Three out of four now installed:
The arrises of the exposed keys were then relieved by chisel:
Next step was to fit wooden plugs into the open end of the dovetail mortises so as to keep the keys from sliding anywhere. These plugs were glued, but if need be could be chopped out at some future point to remove the keys:
Here, all the plugs are in and I’ve just finished scraping the wood to clean up the surfaces of the underside for a final time:
Next I laid out and knifed the trenches for the tapered securing pins in the cap rail:
Out comes the dozuki saw and I begin processing the trenches, which, on the cap rail, go right across:
Some chisel work to remove most of the material:
A paring jig clamped in place, to aid in trimming the shoulder of the trenchway:
Now paring the floor of the trench:
And refining the trench floor with the shoulder plane:
When both trenches were done, I put the top onto the cap rail, and transferred the location of the trench to the top:
Then I separated the top, and used a try square to complete the mark out of the trenches. On the top, the trenches would be stopped instead of though. I used a Starrett precision straightedge right across, connecting both trenches, to ensure that they were perfectly aligned:
After the chisels were laid to rest, here’s what the stopped trenchways on the underside of the top looked like:
Now that the connecting joints were essentially complete, I applied some Tung Oil to the underside of the top. And even coat of finish on both top and bottom surfaces will help, hopefully, keep moisture exchange even on both sides, leading to greater stability over the long term:
In interest of keeping this posting a little shorter, and the loading time for those with slower connections manageable, I will leave pictures of the completed piece until next time, but for now, here’s a teaser:
Part VI .