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Board width for table top

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Forum topic by MichaelT77 posted 10-05-2012 12:25 PM 1733 views 0 times favorited 5 replies Add to Favorites Watch
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MichaelT77

113 posts in 867 days


10-05-2012 12:25 PM

Topic tags/keywords: biscuit joiner board width table

A few weeks ago, I bought some cherry and walnut from someone here in western PA. The man is in his 80’s and has decided to quit woodworking to devote more time to RC aircraft piloting. Anyway, as I was chatting with him about woodworking, he gave me a couple specific tips. He told me that when he was making table tops, he would generally limit board widths to 2-1/2” (and certainly never wider than 3”). And, of course, he would alternate the grain orientation. He’s a big proponent of biscuit joinery, and apparently bought them by the pallet-load.

I know I’ve seen some nice, flat table tops with boards much wider than 2-1/2”.

What do you think? To me, 2-1/2” width is a pretty severe limit.

-- Michael T, Pittsburgh, PA


5 replies so far

View huff's profile

huff

2810 posts in 2039 days


#1 posted 10-05-2012 01:09 PM

Michael,

I don’t think there is a magic number for the width of a board to keep it from cupping. I read many years ago in one of my woodworking books that 6” width should be about the limit in width when edge glueing up lumber for wider panels and it also recommended to stagger the direction of the growth rings. There are a number of factors that will affect how stable your wood is, so I’m not so sure that number is really carved in stone and I’m sure there are a lot of woodworkers that have glued wider boards and didn’t stagger direction of growth rings and their panels or table tops stayed flat. One thing that will help is to mill your lumber and allow it to restablize for a couple weeks before you glue up your panel or table top. Like I said, there are a number of things that will affect how wood moves, from moisture content, width of growth rings, wood stress (that usually affects wood bowing more then cupping, but it still can affect your wood), thickness, etc. All that being said; I always had to work with schedules and time frames, so I usually didn’t have the luxuary of milling my lumber and walking away from it for a couple weeks for it to restablize. So I’ve tried to limit my widths to 6” and stagger my growth rings and “knock on wood” I’ve had good success with wide panel and table tops…..and yes, I have glued up wider lumber and didn’t stagger growth rings a few times and did OK there too. Just remember, wood will always move. We just try to steer it in the right direction when it does, but you’re not going to stop it.

-- John @ http://www.thehuffordfurnituregroup.com

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jdmaher

300 posts in 1334 days


#2 posted 10-05-2012 01:12 PM

I have not heard of such a limit, and I do not agree with that.

I’ve only done a handful of tables, but I use the widest boards that I can afford and get – which is usually 8” – 10”. And I like thick tabletops (at least 6/4).

There is a concern about boards cupping, over time. My answer to that has always been to pick stable woods and let the lumber acclimate a long time (weeks, for me), then choose boards that show absolutely no indication to cup. After rough milling, I let them sit (for at least a few days). Any board that looks like it might someday think about cupping is replaced. When I have a set that looks stable, I mill ‘em again, this time to final thickness. The I let them sit for another few days.

If I have any doubts, after all that, I’d think about re-designing the table with breadboard ends or battens on the underside – but that hasn’t happened to me yet (though I’ve used both battens and breadboard ends for style or function).

I do not alternate grain. Best side, considering both the individual board and matching, is always up.

I’ve used biscuits, and not used biscuits. For me, I don’t see that they add any benefit.

A hundred years from now, some punk might curse me for a fool of a woodworker when a tabletop I made looks wavy. I’ll worry about it when it happens.

-- Jim Maher, Illinois

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HorizontalMike

6968 posts in 1668 days


#3 posted 10-05-2012 02:04 PM

I have read ~7” somewhere before, but as stated earlier this is probably just a guideline. FWIW, my 1846-56 Cherry drop leaf table top and leaves are ~20” EACH and are single boards. The leaves have cupped slightly and the top not at all. The top has the table frame as a support to keep in from cupping and is attached by 6 screws (because wood moves). Notice (here and here) that the 2 side screws are centered across the width of the board and the screws on the outer portion of the width has 2 screws per side at equal distances from the center of the board’s width. This was done on purpose because of wood movement with humidity.

On my blanket chest top, I alternated grains and kept boards around 4” wide. What is important here is that I used cross-member support pieces to prevent warping. How you drill and place the attachment screws on these supports are important. One center and one near each outer end. The outer attachment holes are drilled in two steps:

1. Drill all the way through with a bit the size of your screw (just one size larger).
2. Turn the support strip over and drill from the bottom side 3/4” deep (NOT all the way through) using a bit roughly twice the size of your attachment screw. A loose hole.

By doing this, the wider “bottom hole” of the outside attachment pieces will allow for expansion/contraction of the top without damaging/cracking the top while keeping the top from warping. You can see in the image, I used 4 of these cross supports.

-- HorizontalMike -- "Woodpeckers understand..."

View Oldtool's profile

Oldtool

1925 posts in 945 days


#4 posted 10-05-2012 05:38 PM

I am not an expert when it comes to furniture making, but I have done some research into this as my hobby. I’ve read as many magazines as I could the last 9 or 10 years, and I’ve purchased many books on this subject as well as books on the original antiques, so I could duplicate the finely crafted furniture described as American Period.
What I have noticed is that the early craftsmen used as wide of a board as possible. Many antiques are list on web sites as “single board top”.
To me, the use of many 4” to 6” wide boards (actually some with 2” and 3” boards) looks like a lot of what I see in stores as “Amish Made”, where I assumed they were making the furniture from all the leftover cutoffs from the stuff they keep for themselves.
With that in mind, I am going to be making a dining trestle table for my son & his wife, from three 15” to 18” wide oak boards. I’m going to go with best grain match, regardless of orientation, so the outcome will be as beautiful as possible for them.
I will however, since it is a trestle table, have breadboard ends, and the cross member supports on top of the legs will span most of the width. The top will then be securely fastened down with wooden clips across the two cross members, as well as the center support running down the middle from leg to leg. This is the method I used when I made my other son’s table ( http://lumberjocks.com/projects/66754 )
So if you want to wait about 25 to 50 years for a definite answer from me, I’ll let you know how the oak table comes out by then.

-- "I am a firm believer in the people. If given the truth, they can be depended upon to meet any national crisis. The point is to bring them the real facts." - Abraham Lincoln

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bondogaposis

2765 posts in 1105 days


#5 posted 10-05-2012 06:55 PM

A lot depends on the orientation of the grain. Quartersawn, the width shouldn’t matter much but it is hard to get really wide quartersawn boards anyway. For flatsawn in order to avoid cupping, many folks will rip the board through the center and flip it so that the barksides are on opposite sides of the table. That way any tendency to cup will cancel each other somewhat. I never heard of a hard and fast rule for board width though, I think perhaps besides trying eliminate potential cupping, it was just a “look” that he liked.

-- Bondo Gaposis

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