|Project by linjay||posted 01-30-2016 12:00 AM||631 views||0 times favorited||1 comment|
We bought this table from an antique dealer about 10 years ago. It has a solid walnut top and two 20” leaves. It has a linear screw and crank that you use to make it bigger or smaller. The intent of the original design was that the table length could vary from 56 to 96”. To accomplish this the designer used multiple interlinked slides to connect the 2 ends of the table. . The length of each of these slides was about 32”. Loads were transferred between these slide by 1/2” keys. A single slide consisted of the 2 ways and 2 right angle cross bars—to form a rectangle. The problem with this concept was the cross bar attachment was not capable of maintaining the right angle to the way. As a result the rectangle became a parallelogram – with the ways closer together than they were supposed to be. This caused them to grip the adjacent ways and resist sliding.
Another problem was that each way/slide just wasn’t strong enough to support the actual vertical loads. Even though they were made from some of the nicest maple I’ve ever worked with, they buckled. That is, the sides at the center didn’t stay vertical. It tipped slightly and over time the way developed a permanent curve over it’s length.
A 3rd problem was that the 1/2” keys just weren’t big enough. Theoretically with a 1/2” key you have 1/4” in each piece. But when you factor in multiple parallel running clearances you’d be really lucky to have 3/16” and it could easily be as low as 1/8”.
So the overall design concept forced undesirable design compromises that made the design unworkable. As a result of these problems it had never been possible to easily adjust the length of the table. I never fully understood all of the problems until I disassembled this table.
I changed the design concept to allow a minimum length that would always have one leaf and the minimum table length would be 76”. This was not a compromise. This length suits our everyday needs perfectly. As a result it was possible to have one long slide pair on each side. And each pair has a massive cross section compared to the original. This in turn allowed me to use diagonal bracing to keep the slides parallel and the correct distance apart. Because the slide profile was large it was easy to use 1” keys. As an added benefit the table can now open up to 9’-2” (which requires an additional 14” wide leaf). When I figured all this out I wished I had done this years ago.
All the structural changes were made from free cherry which I happened to have or reworked maple from the original table.
I lubricated the slide surfaces with Simonize floor wax (applied to bare wood). I find this works much better than soap or paraffin wax because of it’s lower viscosity. With the adjusting screw detached you can easily slide the sections with the force from one hand.
The bottom line is my wife is very happy and I had a lot of fun with this project.
-- It's easy when you know how - but that's the hard part. Ontario, Canada