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Extension dining table with hairpin legs and breadboard ends

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Forum topic by Tishman posted 03-07-2017 09:32 PM 1325 views 0 times favorited 4 replies Add to Favorites Watch
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Tishman

16 posts in 647 days


03-07-2017 09:32 PM

Topic tags/keywords: dining table breadboard ends breadboard hairpin legs extension table

Hello!

I’m working on the plan for a dining table but having some back and forth with myself and my wife about the design. I need help! Thanks for reading and did your thoughts.

Known plan so far:

Hairpin legs
No apron
8’ long closed, 42” wide, 7/8” thick.
Breadboard ends
Must be extendable, preferably from the ends, and not from the middle. Ideally, with two 1’ leaves.
Leaf storage under table top in some kind of cleat.

Unknown:
Is there a way to have it extend from the inside of the breadboard ends? That seems impossible, but I don’t know. I can see using dowels instead of a true breadboard end, but that seems like then why bother with them in the first place.

Is there a way to extend from outside the breadboard ends, so that a leaf can be placed on the outside of each one? I’d rather not have alignment pin holes on the outside ends of each breadboard. What’s the mechanism to do that? Build wooden slides from the underside center of the table, with pins that go up to align with holes in the bottom of the leaf? I’d rather make the slides than buy them, as they seem quite simple in my head.

Also, was thinking about putting cross pieces in under the top, perpendicular to the grain of the top, to help wth rigidity. How do I screw those in so the wood can expand and contract? Just drill and screw, but slot all the holes in the support pieces? Do I need to slot the center hole?


4 replies so far

View AandCstyle's profile

AandCstyle

2905 posts in 2095 days


#1 posted 03-08-2017 10:53 PM

Tishman, you can check the Sagulator to determine the amount of sag you might expect without an apron. Normally, the slide out mechanism is hidden behind the apron, but it can be exposed if that is acceptable to you. Also, the slide out ends normally sit beneath the top so I don’t think you will be able to get the clean look you seem to want. FWIW

-- Art

View JBrow's profile

JBrow

1274 posts in 758 days


#2 posted 03-09-2017 03:01 AM

Tishman,

I am no design genus by any means, but after thinking about your design and the “known plan so far”, I am at a loss on how to implement any design that meet all these criteria. The criteria that make the implementation of the design very difficult for me are the no apron, table top dimensions, expandability, and on-board storage of the leafs.

I can think of some methods for extending the table length from 8’ to 10’ on the ends, but these require under the table ugly structures. Since there is not apron, the ugliness has nowhere to hide. The draw leaf table design come to mind, where the 1’ end leafs are stowed under the main top and pulled out when needed, but a main table length of 8’ could make this option problematic.

Traditional center leafs could work to expand the table. The center leaf expansion design would make milling the parts required for the two halves of the divided table top easier. The two sections divided in the center would be 4’ in length and hence easier to mill than the 8’ lengths. But then, the center expanding design would conflict with the desire to avoid center leafs.

In any evet, some further refinement of the design requirements may be in order. It seems to me that to get the dining table you are after will require some further design compromises.

As a start, perhaps determining how many people you will normally seat at the table could be helpful. For example, when I designed our dining table, I decided that under most conditions, 6 people would be comfortably seated at the table. However, we wanted the dining table to be large enough to accommodate 8 people, even though it might be crowed. Additionally, like you, I did not want an apron. However, I did not want the hassle of extending the table to accommodate more people. As a result we settled on a table length of about 7’. Unfortunately during semi-annual parties, some folks must find seating elsewhere. But when we entertain 8 people (about 4 – 6 times per year), there seems to be plenty of room.

If your conclusion is that the extendibility of your table from 8’ to 10’ is an uncompromisible requirement, then an apron of some kind would likely be needed to hide the mechanisms needed to support the end extensions. If a pair of cleats (1-1/2” wide X ¾” thick set on edge) were to be installed on the underside of the 1’ end leafs and secured to the top with through bolts that engage threaded inserts in the underside of the top, then a few bolts could keep the end leafs in places. But the cleats would be visible without an apron and the leafs may not perfectly align with the upper surface of the main top. Additionally, I see no way to provide nice looking onboard storage of leafs with cantilevered cleats installed on the leafs.

I see no way that the extension leafs of the table could house the end extensions and provide the required support when extended, even if the thickness of the top were greater than 7/8” thick and end up flush with the upper surface of the top.

Tommy MacDonald on his “Rough Cuts” PBS program has built a couple of expanding dining tables. Perhaps these table designs could help you refine your design requirements…

http://tommymac.us/2016/01/episode-0411-draw-leaf-table/

http://tommymac.us/2015/08/episode-0602-kitchen-leaf-table-with-tom-mclaughlin/

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Tishman

16 posts in 647 days


#3 posted 03-09-2017 08:58 PM

Hi again,

Thanks for the comments and suggestions! JBrow, I really appreciate the thoughtful advice. Much appreciated. I’ve seen those videos before, and I like the design a lot but I’m not sure my skills are there yet for the draw leaf yet.

I’ve made some design adjustments, and might tweak “these plans” http://mccauleysdesign.com/product/extendingfixed-trestle-table-plans/,
which has an apron and extends from the breadboard ends.

Adjustments to those plans would be:
-Hairpin legs instead of the trestle base.
-Dimensions of 6’ long closed, 8’ long extended, 36-38” wide (still finalizing)
-Probably not using dominos, but rather dowels. I’m not quite ready to drop that sort of $$$ on a Festool Domino at the moment.

Do you think stout long enough dowels would be sufficient instead of dominos? I can elongate the holes in the breadboard ends laterally to allow for seasonal changes.

Thanks again for the help!

View JBrow's profile

JBrow

1274 posts in 758 days


#4 posted 03-10-2017 05:17 PM

Tishman,

Getting the dimensions of the dining table may be the most critical part of the entire project. Unless you know the dimensions you choose will definitely work, you could experience some bitter regrets once the project is finished. Here is a web site that sells table parts but have a nice write-up on designing a dining table. The write-up is consistent what I believe to be true regarding table design. If you poke around on the web, you are likely to find other sites.

https://www.tablelegs.com/resources-how-tos/dining-table-design-basics/

Once you think you have locked in your table top dimensions, you could go one step further and building a mockup of the table top. A sheet of hardboard, MDF, Particle board or plywood cut to the largest dimensions you are considering would be a relatively inexpensive investment. Then drag the mockup into the dining room and set it on some saw horses. If you go with a ¾” material for a mockup, you could even use it for dining a time or two. If the dimensions are not just right then the first mockup could be cut down to a smaller size.

I am not sure to what you refer concerning dominos versus dowels; adding the breadboard to the top or attaching the end leafs.

While I have not incorporated a breadboard into any of my designs, were I to do so, the end of the table would have a short tongue centered in the thickness of the top that is itself about 1/3 the thickness of the top and would run the width of the top (although it could stop shy of the ends if seeing the tongue on the long edge of the table top is undesirable). Several tenons would extend beyond the tongue.

The breadboard end would have a groove with mortises that would mate to the table tongue and tenons. The tenons would be narrower than the width of the mortises to allow for wood movement.

The breadboard end would be installed with glue only in the center, only extending about 2”. The center tenon and mortise would be pinned with a dowel. The remaining tenons would also accept a dowel but the dowel hole in the tenon would be elongated for wood movement. The pinning dowels would only be glued to the breadboard end on one face with no glue on the tenon. Narrow tenons and unglued dowels (except in the very center) would allow the top to expand and contract without cracking or bowing.

On the other hand, if the domino versus dowel references the attachment of the end leafs to the top, I doubt either would be satisfactory. A table whose length is increased with end leafs is a difficult problem structurally and aesthetically. I think of elbows or even someone leaning on the end of the end leaf and worry about the joint of the leaf to the table failing. Also, like you, I would really rather not look at holes in the top’s ends when the table is in the short, unexpanded mode. The center expanding leafs avoid these problems.

One idea for an end leaf design would be to incorporate a half lap joint that accepts the end or the leaf. But even this joint could fail without a pair of cleats running under the leaf and attaching to the underside of the table top. Both the end, which would have the look of the bread board end when installed, and the leaf would mate to the half lap in the end of the top and be attacked with threaded inserts installed in the end and leaf. The end would be removed and the end leaf installed in place of the end board.

Threaded inserts could also be installed in the underside of the top and cleats installed using these threaded inserts and provide additional support to the leaf. I would probably opt for pan head screws or hex bolts to fasten the leaf or end in place. The holes through which the screws or bolt pass through the top would best be elongated for wood movement.

One problem with this idea is that the table top is 7/8” thick. The threaded inserts are 3/8” long. Either the thickness of the top would have to be increased or the half lap become a lap joint, where the thickness of the lap on the top is less than the thickness of the lap on the end board or leaf.

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