Some random thoughts on the dining table project…
The leaf must be hinged in its midsection in order to be stored under the top. I don’t want to see the hinge when the leaf is “deployed,” so it must be hidden when open. The only hinge of which I’m aware that meets this criteria is a Soss “Invisible” hinge. There are other manufacturers, like Sugatsune, but the Soss version is the easiest to find. It comes in two flavors, surface-mount and barrel. Paul Schürch uses the surface mount version; Michael Fortune uses the barrel version. I went with Fortune’s suggestion and, in doing so, I think I discovered why Schürch uses the surface mount.
I used the surface mount Soss hinge years ago and found that it was easy to install as long as you created the properly sized stepped-depth mortise. A plunge router and fence or jig makes it possible. The barrel hinge only requires a hole to be drilled. Easy, right? Yes and no.
The hole is metric, so I had to purchase a 16mm drill bit. Not a problem; I ordered it, along with the hinges, from Lee Valley. The challenge comes when you install the hinge into the hole. It’s a tight fit! Some sanding on the hinge barrel made things a bit easier, but it was still difficult to remove the hinge. I was concerned that if the hinges were too tight, I would damage them on removal. Too loose was not an option, so I opted for a snug fit and only one removal and replacement cycle for test purposes prior to the final installation.
It has worked out fine, but now that everything is together and I’m putting finish on the parts, it’s a bit of a hassle working around the hinges. The surface mount hinges may have been a better option.
Marking part locations
When creating a project with multiple parts that are removed and replaced multiple times, it becomes necessary to mark part locations and orientations. I prefer a marking process that cannot easily or accidentally be removed, so marks made on the surface of the parts are not an option. The method I like involves a Phillips screwdriver and a hammer.
On a surface which will be hidden when the parts are assembled, I punch a small “X” in a corner of the part. I do the same on the mating surface, in the same location. When assembled, the X’s meet. If there are two similar parts, I’ll use two X’s on one of the interfaces to further define the configuration. See the photos below for an example. These are the hinge blocks in one half of the table leaf.
In order for the two halves of the table to extend out from the inner apron assembly, I created a tongue and groove system. With sliding wooden parts like these, harder woods work best. The dining table inner apron is cherry, so the groove material was a given. I could make the tongue from a different material, so I chose hard maple.
I very carefully milled the parts as straight as possible. I used my router table to make the grooves in the inner aprons and used a feather board to ensure accuracy. I milled a 1/16″ deep groove on the inside of the outer aprons to locate the maple tongue. I made the fit of the maple in the groove with about .005″ clearance to ensure a sliding fit but not much sag when the table was open. The fit in the 1/16″ groove was snug.
To create a smooth surface, I put a thin coat of shellac on the sliding surfaces, smoothed them with 0000 steel wool, and waxed them.
I was excited but apprehensive when I did my first test run. I was concerned that the vertical loads on the slides might cause binding of the tongue and groove. I won’t try to describe the details, but if you look at the video you can see that the vertical force of the legs causes a rotation force on the outer aprons relative to the inner aprons.
The binding was bad. The table halves would stick and bind and not move smoothly at all. I was really bummed. I tried increasing the clearance between the parts a little, but that didn’t help. I was so discouraged, I put the whole project on hold (which largely explains the lapse of blog posts this past year).
By the end of summer, I couldn’t put it off any longer. I dusted off the parts and took another look. I stared at the offending parts, the tongue and groove, the built-up gunk that was created at the sliding interface. Then, it hit me. The problem wasn’t the design, it was the finish. Shellac has lousy heat resistance. When I slid the table halves apart, the shellac heated up, melted, and then stuck to itself.
I did some light scraping and sanding to remove the shellac, then applied only wax. I re-assembled the table and…it worked great! Like it was on rails. Like I had ball-bearing slides installed. What a relief. I was back in business.