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Joinery Design Question

Dave Richards

Dave Richards

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SE Minnesota
Here is a table I've been working on. It is based upon the Thos. Moser American Bungalow Square Extension Table. I've been thinking about the joint between the top of the legs and the upper rails and I'd like your thoughts.
americanbung.jpg


Here's a view from below.
americanbungunder.jpg


And a closeup of the way I drew the joinery.
americanbunglegdet.jpg


My thought is that rather than cut the rails in pairs, ie. a front/back pair and a left/right pair, I would make them all identical so that they sort of chain together. The legs would all be identical as well.

The table is an extension table with a single center leaf. I'm not certain yet how the top attaches to the base. I suppose I need to figure out how the extension part works first.

Anyway, I'd appreciate your views.

D
 
That's some ambitious joinery. I think you've come up with a reasonable solution for the interlocking rails and table legs. I'll leave to others to make suggestions for those joints.

The extensions are generally nested sliding dovetails with stops. I couldn't find an image on the web - a good furniture book should have drawings.

How to go about attaching the top rails to the underside of the table is very tricky. You could anchor on only one side of the joint in the top, but that would be flimsy and the legs would be off center when the leaf was in. You could think of using dowels protruding from the bottom of the table top to rest in sockets in the rails. Then you would need to lift the top free from the base for opening and closing. One set of sockets for closed - another for open. Not the most secure setup.

More typical extensions work with rails or aprons that are cut in line with the joint in the top. They stay fixed to each end of the table - allowing the legs to move equally from the center point as the table is opened.

So I guess I'm not helping you find your solution. I can point to the source of the problem, though. Your rails and extensions are shown separate from each other when it would be much simpler to combine them.
 
Thanks Ian,

I think the rails you're referring to are more decorative and perhaps for stiffening the top. The center leaf has a matching rail added, too. The extension mechanism isn't drawn in yet. I can see something it one of the photos of the original but there's not enough detail to tell exactly what it is or how it works.
 
Okay, the legs cannot be separated like on a typical dining table. The lower stretchers prevent this.

Therefore I'm gonna guess that the extensions are attached flat to the underside of the top close to the aprons and that the table top has some sort of dowel or hardware that runs in a groove on top of the interlocking rails.

So, the outer rail or apron is primarily there to hide the extensions from view. It must be cut in line with the joint on the table top. The matching apron on the leaf fills the gap when the table is extended.

I think he must be using metal extensions because wooden ones are quite bulky and require a wide apron to hide.

There, that was my brain workout for today ;)

Good luck with the project !
 
It seems a bit complex to me. Since I have gotten addicted to sketchup (thanks to you), I have noticed I have a tendency to make things more complex than they need to be (at least for me). Don't know if that applies to you or not.

You could make the top rails a half lap and just have a tenon on the leg coming through a mortise in the center. Just a thought.

BTW, I like the overall design. I saw a recent episode of TOH where Nahm went to Thos Moser's shops. Very impressive workmanship there.
 
Ian, I expect metal extension hardware would be right for this table, too. Here's a view of the table with the leaf added. I suppose the extension hardware could be attached to the rails. I need to hunt up some hardware for that.

americanbungExtended.jpg


Travis, complex? Are you kidding? The letters after my name are PhD-OE. The "OE" stands for Over Engineer. :D In this case though, I was trying to think up a simple way to maintain the detail, gain some strength and make the joints as easy to cut as possible. My thought is that all four rails would be identical (Until the point of adding the extension hardware.) and I wanted the outside corner detail of the leg to be as strong as I could make it so I wouldn't break it off. Here's a close up view of the joint assembled.

americanbungjoint.jpg


Now I'm thinking I could drill a hole in the end of the leg and fill it with epoxy, redrill and tap for a bolt or machine screw to hold it all together.
 
Modified leg joint.

I decided to skip having the leg running up between the rails. Now I have a single tenon and motises through the a bridle joint in the rails. Better?

americanbungNewLeg.jpg
 
Now that makes sense to me, I've been thinking about this thread since I first noticed it. Now maybe you could put a dovetail slot in the rail for the table top to slide in. Then a matching slide on the table top to keep the top in alignment when you open it..:thumb:
 
Dave
Is there a reason that the leg tenon needs to come up through both rails? I guess if I were doing it, I'd do the half laps like you have them but only put the square hole for the tenon in the lower piece. I guess it wouldn't matter either way, but it seems like a bit more extra work to run it through both.
 
Doug Shepard said:
Dave
Is there a reason that the leg tenon needs to come up through both rails? I guess if I were doing it, I'd do the half laps like you have them but only put the square hole for the tenon in the lower piece. I guess it wouldn't matter either way, but it seems like a bit more extra work to run it through both.
Click to expand...

I've been thinking about the legs too, Doug, but I was thinking that they might need more reinforcement. Legs are subject to a lot of knocks - from feet, from vacuum cleaners and from being dragged across floors.

I'm worried that the through-tenon might get loose with wear. If it was my table I'd flare the mortise on the upper piece, saw a couple of kerfs in the end grain of the tenon and insert wedges. That would "suck" the entire joint nice and tight and lock it. It's a difficult joint to clamp properly, so I think the addition of the wedges would add some mechanical strength.
 
Ian, you've got a point there. If you wear a hat nobody will notice. :D

Actually, I agree with your thought on wedging the tenons. I thought about it when I was editing the drawing but decided not to draw the wedge yet.
 
Better, much better. It is too easy for me to over engineer with sketchup. If you remember the dresser I drew up, when I got to building to box compartment, I was like "why in the h*ll am I doing it this way?". Changed it on the fly, but it is a whole lot easier to draw than cut wood.

When you going to build this Dave? You going to do steam bending or laminations for the curves?
 
Travis, I'm glad that looks better. I do miss that little detail of the leg extending up into the corner between the rails, though.

I suppose I would do lamination for the bent rails. My understanding (and I'm probably wrong) is that cherry doesn't look so wonderful after being steamed for bending.

The table will get put on the list of stuff to build. The problem with SU is I can draw stuff way faster than I can build it. I probably should buy some cherry, too. That'll have to wait until spring so I can get my utility trailer out of the snow bank. :rolleyes:

Of course there's parts for the boat to work on and a new boat I want to start. Bookshelves for my son's room and for the office. I've got so much to do I don't have time to go to work! :D
 
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