Single Board Tabletop

jacon4

jacon4

Well-known member
Merry Christmas everyone,

I just got a walnut slab to make a new tabletop for a period QA table, Anyone have any experiences/ suggestions with building single board tabletops. This top will be
24"W X 44" long or so, i would like to avoid cupping and or splitting of the top. Breadboard ends? no breadboard ends?  Anyone here tried chemical treatments like PEG/ Pentacryl prior to construction?

Thanks, james
 

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  My experience with table tops,has taught me to use stable(straight grain) dry(air dried works for me) with a little age on it (3yrs.+). I use antique minwax oil, on the whole board,top,bottom,ends.And really soak it, 3 to 4 applications,followed by quality paste wax. Tried this method highly figured wood,seems to work pretty well,especially on walnut. Repairs,and renewal with this method are Duck Soup!

                                    Your buddy Ed
 
James,
A single board top doesn't act much differently than a multiple board top. Wood moves across the grain, plan for it.
Mike
 
Although not a single board table, I still intend to reproduce in my lifetime a table a friend of mine made years ago, he called it an Irish wake table-just really a longish(6-7 feet) oval drop leaf table made up of 3, 18-19 inch wide boards with long rule joints joining the three planks and 8 (4 swinging)cabriole legs for the support.
Anyway, he used what I thought was a pretty ingenious method to guarantee there would be no cupping across the grain on the two "floating leaves". On the underside of the table, he had cut 2 or 3 long sliding dovetail channels cut across the grain, into which he had slipped waxed dovetailed "sticks" or "strongbacks"into the slots to resist any tendency for the wide plank to cup-then the ends of the dovetail mortise are plugged.
I liked this method so well I have used it on some 4 foot long drop leaf tables I have made, so those free floating leaves will surely stay still. I even used one on a handkerchief table-it has a 19 inch wide floating leaf.
Make sure the plank is well seasoned(3yrs like mentioned above is really necessary), be very skeptical of any kiln-drying, put two of those sliding dovetails across the grain, and I will guarantee it will behave.
I can post a picture of the underside of the handkerchief table leaf, if desired.
 
Sorry. I forgot. That is a fabulous board and is the necessary first step to building period furniture. That fine, close grain with light curl is perfect for any period tabletop.
I think what I was describing earlier could best be described as a batten attached with a long sliding dovetail. Make sure and don't cut you dovetail too deep and weaken the top, a 5/16 deep tail will hold. And, of course remember to leave it waxed and not glued, so the top can come and go freely.
 
LOL @ "and I will guarantee it will behave."


Thats what i wanted to hear! Interesting idea on sliding dovetails. This slab is pretty stable, it was air dried for 4 years and when it reached 20% MC, kiln dried down to its present 10%. As an owner of several period colonial pieces, almost all of them have "issues", mostly shrinkage cracks on very wide timber. I just want to do everything i can to avoid that happening to this top.

Heres a pic of where this top is going, its a period QA american highboy base, i was attracted to its "neat& plain" form as well as its original hardware. Although not real valuable because its missing its upper case, i want to give it a new life as a small server.
 
I am Irish and I have restored many wake tables and have also made about a dozen in Elm, Mahogany and Oak. Mikemcgrail, I would suggest that, given their thickness, the dovetail strengtheners would be no match for the power of a cupping board. If the leaves have remained flat, then it is more likely due to sound material selection and seasoning than any joinery trick.

James, wide unsupported leaves are nothing new, I would recommend aclimatising the timber specifically for the environment where the tables will reside and then proceed accordingly.
 
Thanks guys, this server wont let me post the pic even though its under the limit, guesses there is a daily limit as well. I'll try again tomorrow
 
Of course material selection and seasoning are more important. Surely no one would build a large flat floating piece from poor material that had not been seasoned. I have never built a period table from elm or oak, and would consider the modern stock that is available in these species that I have seen here as unsuitable for a fine table.
The piece of walnut jacon4 has pictured here is very fine grained, and if allowed a suitable time period, it will behave. I would guess it to be one or two boards away from the pith, and while it will have a great propensity to cup whilst drying, it should be fine after a few years.
As for the batten not providing any resistance to cupping, the fine cuban mahogany tilt top tables almost all have some sort of batten affixed to the bottom, I just think trapping it in sliding dovetail will give greater strength and  allow for the come and go of a 20+ inch wide board. I agree that I am not sure any thing could hold some of the pieces of modern elm or modern oak I have seen, I am pretty sure it will hold that piece of walnut.
If that piece happens to be a little extra long, you might saw a foot or saw off the end and then resaw that piece to make sure the wood has been kiln dryed correctly. If you can resaw quarter inch slices 8 or 9 inches wide and they behave, you will be safe.
 
I will throw in my (two sence). I would think that if you cut a sliding dovetail with a dovetailed batton and then WAX it. It would slide where ever you would want it to. The next question should be how deep to cut the dovetail without undermining the top, what ever wood it may be (waxing the dovetail)? fasten it on one side, or in the center and let it shrink from there. Once you wax the dovetail I know of no glue which will secure that joint by itself now or in the future. If you are going to wax the dovetail, leave 3/4" on each width edge and run away. I did not mean run away I said that in haste. Actually you could walk away slowly, you have plenty of time. At least a few seasons. Do not set it near a forced air heating duct. Now this is what woodworking is all about. How do you hold one board's movement, cross grain, against another. It's no simpler than that. Once we get that perfected we can close this site and go home (actually I should have said go to our workshops).  Seasoned wood might be a first step in stability. In either case I would only cut a half dovetail on either side of the top and battons. Less work less time same stability. This way you can run further away and not have to worry that it was your joint. Please take this in the mannor it was meant. This joint, in either case, will last longer than most of us. Seven years from now while you are laying in bed, in the winter, and you hear a loud snap you will realize that you should renewed your SAPFM membership for upcoming year. So why wait, renew today.
 
Jacon4,

If you are are looking for a traditional method of holding the top flat, I think your choices are either a breadboard or battens screwed to the bottom face. I've considered the dovetail idea before, but talked myself out of it: a 7/8" top with 5/16" channels cut across the grain is, in reality, only  11/16" thick. (There is just a lot of extra material on one side). It is more than likely that the top will move after you cut the channels because you are removing material from only one face. For a dovetailed batten to be effective, it will have to fit very tightly. It has been my experience that over time, even tight-fitting waxed parts will 'gel' together and sieze and it would then be easier for the top to split than to overcome the friction necessary to slide along a dovetailed way. Having said that, it is obvious from Mike's post that somebody is using the dovetail method and getting away with it, at least for now. I'll throw my two pence in with Jeff.
 
Yeah, now that i think about it, i have a federal period 4 drawer chest of drawers, single board construction, the two sides of case are dovetailed into the bottom of  top, stopping just short of the front and yup, the top split sometime during its life. By the time i got the chest that split had been professionally glued and its barely noticeable but its there, although i am pretty sure that the dovetail was glued  and did not float.

It may just be that with single board construction there are gonna be issues no matter what you do or how careful you are. Hopefully, heres a pic of where that slab is going.
 

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Here's my 2-cents worth: I've had many ruff wide boards that were extremely flat.  However, as soon as you plane both sides they would cup (within 24 hours).  I've also seen many tops with bread board ends that would also cup.  You also will have the unsightly look of the ends when it expands & contracts (customers don't like this look).  Screwing a batton with elongated screw slots to the bottom works the best for me.  I've had wide boards cup when a dado is plowed across the grain.  If this happens a dovetail slot 5/16" deep will not keep it flat.

Dennis Bork
Antiquity Period Designs, Ltd.
 
Sorry to cause such a controversy. I guess I cannot guarantee what will happen forever. I will include a scanned photo of my mentors original wake table, made prior to 1972. I have used this construction on at least 3 tables myself, but never as large as his original. MIne have not split thus far, and my tables were made about 15-20 years ago. His table is now about 30+ years old and was still sound in 2005, the last time I saw it. While I suppose the sliding dovetail could possibly tighten over time, the direction of the top grain should not cause any shrinkage to tighten it. I guess I am just predisposed to like the ideas of my old friend, I thought(and still think) he knew walnut better than anyone.

 

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James- You can account for the expansion and contraction easily with the ideas of the other members, but your real enemy is warping. I think the best way to be able to control thr potential warping is to make the top as thin as your design sense will allow. Alot of these tops are 11/16 or even 5/8. You have a better chance to control warping in a thin board because it doesn't have the power of a thick one. I would attach it at the front and let it expand out the back. If you put a batten and fasten it in the middle and slot-screw the ends I think you'll be OK. Make the batten as beefy as will fit, which is not too thick in your case because of the draws underneath will crowd it. Use maple or something tough.
The tops that are dovetailed directly onto the vertical sides of pieces are usually done that way because there's no top draw blade and so no room for any other method. The tops will expand the same way as the sides, so they could have been glued with no ill efffects.-Al
 
THANK YOU to all that commented.

Although still undecided on breadboards, battens or dovetails, i will stick with traditional joinery as i am to chicken to try those new chemical treatments i have been reading about. They were developed by conservationists who came up with a way to keep ancient wooden ships that were sunk, and treated chemically  after they were raised to keep the wood from disintegrating when exposed to air. It sounds very promising in future though as a means to prevent splitting/cupping in single board construction.

HAPPY NEW YEAR EVERYONE
 
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