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Improving this dining table base

2K views 34 replies 17 participants last post by  Erik07 
#1 · (Edited by Moderator)
Hi there.

I just completed a mockup of this white oak dining table for a friend. The base itself (what you see from eye level) is what my friend is after.

All components are 1.5×3.5 and the proportions seem fine in the mockup. However, the upper long stretcher and three cross-supports aren't doing anything to prevent twisting/racking.

Looking for your suggestions on how to stabilize the table without changing the "look" of the base.

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#5 ·
Since you don't list the dimensions of the table top, I'll take a guess that it's a good sized table-say able to accommodate 6-8 people at a meal.

If that's the case, I'd try to persuade your friend to reconsider the base. The way it's sketched out, people at the table will have a real challenge finding room for their feet-when they pull their chairs up to the table to dine.

If this is in fact an idea from a table with a steel base, it might be that that steel members are narrow enough in dimensions to support the weight of the table without seriously reducing room for feet. But even having said that, the space under the table with the base designed as shown is a little busy looking.

Just my opinion, but if you view lots of dining room tables, the supporting structures are usually designed to maximize the space under the table for either diners feet, or chairs pushed into the table when not in use.

Gerry
 
#6 ·
I don't think that the size of the members and the joinery are adequate to resist twisting and racking. Even if the size of the members increased and the joinery were interlocking, there will be extreme twisting and racking forces that will eventually cause joint failure. I agree that the bottom members laying flat on the floor are going to have issues with the slightest unevenness of the floor. Some adjustable feet are needed.
 
#7 · (Edited by Moderator)
Taking another look, in addition to the other suggestions about feet, oak is heavy as hell. If that is 8' x 44" x2" it'll weigh in excess of 200 lbs. alone and you can't rule out that a couple of 200lb men might sit on it. Never seen a dining room table you couldn't sit on. I think that base has to be metal. A wood base would need to be like 4×4 beefy with a few cross braces under there in both directions and some rock solid joinery and that would ruin the design. Also, those cross braces could also double as c channel.

As far as seating, I think people would have no problem sitting at that table. Maybe even better than most. Your feet wouldn't go anywhere near the centerline and because there are no legs at the corners 2 people could sit at each end. I like the design because of that.
 
#8 ·
The real test of good design is in how well the piece performs in its intended use. If it looks attractive, but is limited in use because of some unforeseen flaw, then the design isn't workable.

If it was me, and since the supporting structure members are 1.5×3.5, I think the plan calls for a real mock up using dimensional framing lumber. Pick through the stack at the big box so it will be straight. Put it together; screws are fine for this purpose and then get some chairs and move around it, sit at it, and so on. Use sheet goods for the top.

I'm less concerned about twisting and racking of the top. If you use properly dried stock, I think it should remain flat. Consider bread board ends for the top.

I think those corners could be "tippy" in this configuration. I realize that it would take a lot, but crazy things happen when company comes over.

The floor contacting surface of the supporting structure is very likely to rock at least a little as designed in the drawings. A truly flat floor is a rare thing. I would modify the design to get the long cross members on the bottom up off the floor maybe 1/2 or 3/4 of an inch.

As for joinery, I'd use double bridle joints for the corners of the vertical support structure, half laps for the cross pieces supporting the top, and I'd mortice the two verticals on the long cross piece where they come up to meet the supporting cross member structure under the top.

I don't have a domino machine, and have never used them. My sense, though, is that I just wouldn't trust it to handle the joinery in this heavy piece.
 
#9 ·
The real test of good design is in how well the piece performs in its intended use. If it looks attractive, but is limited in use because of some unforeseen flaw, then the design isn t workable.

If it was me, and since the supporting structure members are 1.5×3.5, I think the plan calls for a real mock up using dimensional framing lumber.
Best answer in the thread!

I to have doubts but there is nothing like testing the idea and seeing it in action. Lot of people do things I never thought would work and odds are it didn't work the first time they tried it either.
 
#10 ·
That design depends on a dead flat floor. Something that rarely exists. The corners are not stable either. If someone leans on a corner the table is going to tip. Nobody will be able to sit at the center of the table because the legs are in the way. I would re-design it.
 
#11 · (Edited by Moderator)
If it was me, and since the supporting structure members are 1.5×3.5, I think the plan calls for a real mock up using dimensional framing lumber. Pick through the stack at the big box so it will be straight. Put it together; screws are fine for this purpose and then get some chairs and move around it, sit at it, and so on. Use sheet goods for the top.

I m less concerned about twisting and racking of the top. If you use properly dried stock, I think it should remain flat. Consider bread board ends for the top.
Already built the mockup (see my original post). It's built from dimensional lumber I dressed on the jointer/planer. Their are two dominos at each corner joint with half-laps in the expected places. The base is solid at these joints, but when I put the top on (8' x 40") it wants to twist - not stable at all. We'll rethink the base.
 
#12 ·
I think the table she's trying to copy had a steel base. Are you thinking that this joinery won't work in oak? the base is connected with dominos, and it feels strong enough to me.
Taking another look, in addition to the other suggestions about feet, oak is heavy as hell. If that is 8' x 44" x2" it'll weigh in excess of 200 lbs. alone and you can't rule out that a couple of 200lb men might sit on it. Never seen a dining room table you couldn't sit on. I think that base has to be metal. A wood base would need to be like 4×4 beefy with a few cross braces under there in both directions and some rock solid joinery and that would ruin the design. Also, those cross braces could also double as c channel.

As far as seating, I think people would have no problem sitting at that table. Maybe even better than most. Your feet wouldn't go anywhere near the centerline and because there are no legs at the corners 2 people could sit at each end. I like the design because of that.

- Andybb
Thanks Andybb - great insight. I also agree that the legroom is great here. In fact, that's the reason my friend chose this design. But I'll have to rethink the base - it's just not beefy enough.
 
#13 ·
If it was me, and since the supporting structure members are 1.5×3.5, I think the plan calls for a real mock up using dimensional framing lumber. Pick through the stack at the big box so it will be straight. Put it together; screws are fine for this purpose and then get some chairs and move around it, sit at it, and so on. Use sheet goods for the top.

I m less concerned about twisting and racking of the top. If you use properly dried stock, I think it should remain flat. Consider bread board ends for the top.

Already built the mockup (see my original post). It s built from dimensional lumber I dressed on the jointer/planer. Their are two dominos at each corner joint with half-laps in the expected places. The base is solid at these joints, but when I put the top on (8 x 40") it wants to twist - not stable at all. We ll rethink the base.

- inexile
Ok; when I read (and re-read) your post, I noted that you did say mockup, but since there wasn't a picture of the physical mockup I took it to mean that it was in drawing only.
 
#14 ·
I think that the center backbone needs to be much beefier to resist twisting or flexing. If you clamp one end and can flex it at all using some leverage, it is not strong enough. I would also us bridle or finger joints to join the vertical legs to the horizontal base so that you can put a foot or pad there to elevate the horizontal pieces off the floor they don't act like runners on a rocking chair.
 
#15 ·
I think that the center backbone needs to be much beefier to resist twisting or flexing. If you clamp one end and can flex it at all using some leverage, it is not strong enough. I would also us bridle or finger joints to join the vertical legs to the horizontal base so that you can put a foot or pad there to elevate the horizontal pieces off the floor they don t act like runners on a rocking chair.

- Lazyman
Thanks Lazyman. So what if I thicken the backbone to 2" (from 1.5") and all of the other base members to 1.75" and change from mortise/tenon to a bridle join for the base connections? I also need to raise the cross members so they're not flat against the floor.
 
#17 ·
Not an accomplished furniture maker here but it looks to me that the cross members at each end that are joined to the center backbone will flex a bit. Applying pressure at one corner will cause the opposite corners on the top to flex up in my opinion. Just a little flex over a large top will be exaggerated somewhat like winding sticks. If you can make it work and be solid I will tip my hat to you. My vote is on metal legs with maybe a diamond shaped rail joining the legs under the top.
 
#18 · (Edited by Moderator)
Not an accomplished furniture maker here but it looks to me that the cross members at each end that are joined to the center backbone will flex a bit. Applying pressure at one corner will cause the opposite corners on the top to flex up in my opinion. Just a little flex over a large top will be exaggerated somewhat like winding sticks. If you can make it work and be solid I will tip my hat to you. My vote is on metal legs with maybe a diamond shaped rail joining the legs under the top.

- controlfreak
If that joinery isn't "locked" it's going to flex…
 
#19 · (Edited by Moderator)
2" probably would be the minimum I would consider. Traditional tables have wide aprons to support long or wide spans and you need extra strength to make up for the lack of aprons, especially since the design leaves those hanging corners. Most hardwoods will be stiffer than pine so that could a factor as well. You can taper the spine after the last wing to hide the thickness. Making the spine a little wider might help as well. How the wings are connected is another factor. Just connecting them to the sides of the backbone with tenons, especially a loose tenon may not provide enough stiffness either. It may want to flex there or at least weaken the tenon joint over time. I think that I would want to use a half lap and have the wings be a single piece that goes across the entire width. That should also improve the stiffness because the opposite side of the top will also help to resist flexing-as one size tries to flex down, the top on the other side helps to resist it. I didn't catch how thick the top is but a thicker top will help too. Another pair of wings between the center and the end wings sort of like battens probably would not hurt either. Note that the joint of the wings to the top needs to account for wood movement across the length-screws from underneath with enlarged holes in the wings for example.

All theoretical of course. I have not made something like this so I am just relying on observations based upon how I have seen wood behave.
 
#21 ·
2" probably would be the minimum I would consider. Traditional tables have wide aprons to support long or wide spans and you need extra strength to make up for the lack of aprons, especially since the design leaves those hanging corners. Most hardwoods will be stiffer than pine so that could a factor as well. You can taper the spine after the last wing to hide the thickness. Making the spine a little wider might help as well. How the wings are connected is another factor. Just connecting them to the sides of the backbone with tenons, especially a loose tenon may not provide enough stiffness either. It may want to flex there or at least weaken the tenon joint over time. I think that I would want to use a half lap and have the wings be a single piece that goes across the entire width. That should also improve the stiffness because the opposite side of the top will also help to resist flexing-as one size tries to flex down, the top on the other side helps to resist it. I didn t catch how thick the top is but a thicker top will help too. Another pair of wings between the center and the end wings sort of like battens probably would not hurt either. Note that the joint of the wings to the top needs to account for wood movement across the length-screws from underneath with enlarged holes in the wings for example.

All theoretical of course. I have not made something like this so I am just relying on observations based upon how I have seen wood behave.

- Lazyman
The wings (thanks for the right term here) are single pieces connected to the spine with half laps. I've only screwed them together in the mockup - adding glue to the thicker, oak members should take some of the flex out. I like your idea of adding two more wings. as they're invisible when standing or sitting at the table. They top will likely be 1 1/4" thick, though I could do a thicker top and add a heavy chamfer to the underside to make it look less chunky. Screws with enlarged holes for sure.
 
#26 · (Edited by Moderator)
Looking for your suggestions on how to stabilize the table without changing the "look" of the base.

- inexile
^This doesn't seem that difficult to read.

Table Furniture Rectangle Outdoor table Outdoor furniture


- LeeRoyMan

Keep in mind seating room-make sure there s space for a chair to slide in if you add "wings" for additional support! You don t want people sitting at the table to have to straddle the support.

- PCDub
But some like to draw up there own changes while missing the two prime directives.
 

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