I need advice on the construction details of a round table top that will be about 6 feet in diameter. The base will be wrought iron. The top will be made from old oak barnwood siding that is “distressed”, with old rusted nail holes. This weathered wood is cupped, so even with ripping it, planing it and edge gluing each piece back together, the final thickness obtainable is barely 3/4 inch. (possibly only 11/16) I want the edges to look thicker. I also have old oak 2×4’s from this barn that could be used to make an understructure that would create an edge thickness of almost 2 inches (more than I need). I just want to avoid cross grain construction that would constrain the movement of the top.
If I build a large octagon, jointed with splines, place the top on it, trace the circular outline and cut the circle with a jig saw out of the 2×4’s, I could attached it under the top with slotted screw holes. The problem is that as the top expands and contracts, it will no longer line up with the 2×4 layer. Any advice would be appreciated. Thanks
Jay
Replies
While it's a bit more jointing, you can create your "undermount" with short lengths of the 2x4s with the grain all running the same as the top. These could be just glued to the bottom of the top boards so they would move together. Alternatively, the 2x4's could be the actual frame for the top, with the rest mounted inside as a floating panel (or panels). See the outdoor table in FWW issue 183 for something similar.
Interesting idea. If I did it as a floating panel, wouldn't there be a step off from the edge of the frame down onto the panel, since the panel would have to sit in a groove? How would you do it and keep the top surface of the frame flush with the top surface of the panel?
Thanks.
Jay
The tenon on the insert pieces, and the dado to receive the tenons can be made to line up exactly when the surfaces are flush. There does have to be a small gap in the surface--to allow for movement, but it doesn't have to be an entire tapered edge, it can be a square edge rabbet.
I'm sorry, I'm not visualizing this. Can you make a sketch and scan it? Thanks very much.
Jay
Scanner has gone south, but I'll try a different word sketch. First join the thinner wood and cut the circle--a little oversize if size is critical. Then, with flat and edge jointed pieces of the 2 x 4 glue them both to each other and to the thinner top with the grain all running the same direction as the thin top. You are essentially gluing a "donut" of thick wood onto the under side of the top. You will probably have to work in stages to have firm clamping surfaces. Then make the final trim of the circle, trimming the undermount donut to be flush on the edge with the top.
That sounds easy enough, but do you think that donut of 2x4's will keep the top flat? Since the grain all runs the same way, it would be subject to the same tendencey to bow as the thinner top. When you did yours what kind of wood was it? Did you alternate growth rings up and down when edge gluiing?
Jay
It will of course have to be fastened to some sort of underpinnings. We have been told there is a cast iron base. Is this just a pedestal, or does it have legs, etc. If there is just a pedestal you would fasten it the same way as a tilt top table, with a block glued to the top, with stretchers underneath running cross grain (allowing wood movement in the outer screws) The hidden stretchers work to keep warping down. If there the cast iron base consists of legs on a frame, the top can be attached to this. Firmly attach the centers and let the width be able to move with the seasons.
I would not alternate the growth rings. It should be easier to control one big warp that a series of washboarding. Besides, if you do that the "donut" would end up looking very choppy and cobbled together. That's true, but you don't want to advertise it. Let people have to get down on their hands and knees to figure it out.
The base is probably going to be some sort of pedestal. My wife and a designer are looking at options. I think the crossgrain stretchers with elongated screw holes sound like a good idea regardless of what the base style is. Thanks.
Jay
Oops, I think I "sketched out my other idea. For a few pictures of the "floating" top, go to the magazine tab and do a search for back issue 183. You would be looking for plans for an exterior table.
Jay
An easy solution would be to make another smaller circular top, used as a base. You could use regular oak if you don't have enough of the original wood. Finish it to look alike, and when you attach the 6' diameter top to say, a 3' diameter base, align the grain direction of both circular pieces. You can still create slots for movement, but at least the top will be expanding and contracting in the same direction. Then, with a T-shaped cross brace underneath the smaller section, you can slot it for movement. This will lend a tremendous amount of extra support to a thin table top with that large of a diameter.
Walnutz
Yes, that would support it, but it would not create the visual impression that the top is thicker than 3/4 inches. How would you achieve that? Thanks.
Jay
Jay
If you want to beef up the edge, to say 1 1/4", just do it. Glue on extra thickness just around the perimeter of the table, and flush trim with your router. It wouldn't be as nice looking as having thicker stock, but you already stated that thicker stock wasn't an option. I don't see that you have any other choice in the matter.
Walnutz
Edited 2/6/2007 1:42 pm ET by Walnutz
Jay,
I've done this in a very simple way..not sure it's the correct way...but five years later no problems: Glue up about a 7'x7' panel and cut your circle out with a router. Take the waste and, taking a chunk out of the sides, slip it back under the edge about 2" all the way around...and glue. Recut circle with router...done. In my case the panels and grain lined up well and I didn't have to worry about expansion or contraction...and I could not see a seam.
Edited 2/6/2007 2:00 pm ET by BG
I think you're making a mistake in trying to make a silk purse out of a sow's ear. Better to make a really nice sow's ear purse. So.... using more of the siding, use several layers to build up the thickness. Then the edge will have an old wood look that is all from the same family. Don't try to match grain, color or whatever. The more discontinuous the match the less it will matter.
It wouldn't be too hard to make two layers, but I am concerned that without some sort of frame (in this case a circular frame) it will bow will be impossible to keep flat. A six foot diameter circle is quite big. Also, the edge would me mostly endgrain. If the table were rectangular, you would use a breadboard end to keep it flat. Anyone, please comment on this point.
Thanks.
Jay
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