How are pieces of wood joined together?

When I see large pieces of finished lumber, say a piece of 1" thick oak thats a foot by 4 feet, it seems to be made of several pieces joined together. Is this done because smaller pieces are cheaper or is there some other reason? How are these joined together, is it by bisuit joiner method or something more exotic? Will bisucit joined lumber be as strong as lumber joined together in other ways?
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The wood is glued together (called edge gluing). Biscuits, dowels, splines etc. provide assistance in aligning the pieces and add some strength, but its the glue that does the job. A biscuit is one of the fastest and more reliable ways to add this alignment assistance.
Wider pieces of lumber are expensive and less available. Also, if you use power tools for milling the lumber, width capacity translates to more expense in the tool (initial cost plus ongoing blade replacement). The primary culprit here is the power jointer. blade prices go up exponentially with increases in width.
For furniture purposes, a glued board is as strong as a single piece of wood. In fact the glued joint is usually considered stronger the wood. Bob
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glued up pieces are also less likely to split, or so says Norm.

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Narrow wood is easier to come by. There are few trees still to be harvested that will yield very wide boards. Wide boards seem to warp easier but I don't know what the optimum size is.
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wrote:

Some folks rip wider boards into smaller widths to minimize movement. The grain is flipped with each alternating board so that if the wood cups, it is less likely to cause the entire table to cup. The optimum width I've heard for this is 4", but that may vary from person to person.
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On 1 Oct 2004 18:30:51 -0700, snipped-for-privacy@hotmail.com (ississauga) wrote:

This is very common, although I'd be a little surprised to see oak treated like that, in those sort of sizes. There are several reasons to do it.
It's done for several reasons. Go to Ikea and look at their "solid timber" products. These are nearly all thin strips of rubberwood glued together, no more than an inch or two wide. Rubberwood is a popular timber these days because it's sustainable (and not a bad timber). When trees on a rubber plantation are worn out, they're now felled for timber. They're only small though, so they must be joined together to make a useful board.
In foot-wide oak, then you don't need to do this. Oaks are quite large trees and sawn boards will already be this sort of size. You can buy solid one-piece oak quite easily.
The problem with oak is that of timber movement. If you cut any flat-sawn board, it tends to curve on drying - the rings in the tree tend to go straighter.
One solution is to only use radial boards, which don't curve. In medieval times this was done by splitting the tree rather than sawing it (also easier work) to give very stable "riven" boards, unfortunately wedge-shaped. Around 1900, the fashion was for quarter-sawn oak timber, where consistent flat boards were sawn as a good approximation of being radial. This is expensive sawing work, because you need to keep turning the log round for each new cut, and also because there's more timber lost as waste.
So if you're looking to build non-warping furniture from flat-sawn oak, the usual solution is to saw the board narrower, then put it back together. This would usually be done in the workshop though, not at the timber yard. Boards are re-assembled either in the same order, or more usually alternated up and down, so that any small warp that does form becomes an even smaller "wiggle" instead. The width of the boards used depends on the application, the thickness and the quality of the timber. Boards flat-sawn from near the centre of a log are comparatively stable (they're almost quarter sawn anyway), those near the surface are less so.
For joining them, then it's done with glue. It's a long joint of the long-grain face of the timber, so it's a strong join. Commercially (Ikea) it's done by a huge machine. Commercially (small furniture workshop) it's done by a manual clamping jig called a "panel press" (search for "Plano", as the best-known maker). If you wish you can also do it with biscuits. Biscuits add little to the strength, but they make alignment easier if you only have bar clamps to hold it together and not the alignment abilities of a press.
If you want to know more, any cabinetry book will tell you, or I recommend Hoadley's "Understanding Wood" or the US Government Forest Products handbook (paper copies available from Lee valley, or read it as free PDFs on-line)
--
Smert' spamionam

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[...]

Which gives rise to the question why you never see boards made from two suck wedge-shaped ones glues together to form a rectangular slab?
--
Dr. Juergen Hannappel http://lisa2.physik.uni-bonn.de/~hannappe
mailto: snipped-for-privacy@physik.uni-bonn.de Phone: +49 228 73 2447 FAX ... 7869
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On Sat, 02 Oct 2004 16:44:55 +0200, Juergen Hannappel

if you have the technology to get riven boards flat enough to glue them together you almost certainly have the technology to saw the board you want out of the log.
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snipped-for-privacy@thanks.com writes:
[...]

Ok, riven boards are to "wavy". But if you saw the trunk into wedge-shaped boards you would have only true "quartersawn" surfaces, and could then glue them up to rectangular-sectioned boards, with minimal losses.
--
Dr. Juergen Hannappel http://lisa2.physik.uni-bonn.de/~hannappe
mailto: snipped-for-privacy@physik.uni-bonn.de Phone: +49 228 73 2447 FAX ... 7869
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On Sat, 02 Oct 2004 16:44:55 +0200, Juergen Hannappel

That is a _very_ good idea....
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On Sat, 02 Oct 2004 18:37:29 +0100, Andy Dingley

why?
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On Sat, 02 Oct 2004 11:30:31 -0700, snipped-for-privacy@thanks.com wrote:

Because I have a froe, a lot of logs too narrow to quartersaw, and an idea...
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On Sat, 02 Oct 2004 11:30:31 -0700, snipped-for-privacy@thanks.com scribbled:

More QS wood from the same tree (less waste), wider QS planks from the same tree. The only disadvantage I can think of now is that the edges of the plank would have a glue line.
Are we missing something? Why hasn't it been done? Is it a question of cost, i.e the effort is not worth the additional wood? Or did Juergen have a true inspirational moment?
Luigi Replace "nonet" with "yukonomics" for real email address www.yukonomics.ca/wooddorking/antifaq.html www.yukonomics.ca/wooddorking/humour.html
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Luigi Zanasi said:

While cutting up some pin oak the other yesterday, I wondered the same thing. I had all these wedge shaped pieces left over - what could I do with them, rather than the fireplace?
FWIW,
Greg G.
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[...]

I definitely did not have a true inspirational moment, because the idea is not mine but rather comes from an aegyptologist whom i happen to know , so maybe it's a *very* old idea indeed...
--
Dr. Juergen Hannappel http://lisa2.physik.uni-bonn.de/~hannappe
mailto: snipped-for-privacy@physik.uni-bonn.de Phone: +49 228 73 2447 FAX ... 7869
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On 1 Oct 2004 18:30:51 -0700, snipped-for-privacy@hotmail.com (ississauga) wrote:

It is more difficult to obtain wider boards than 100 years ago narrower boards are glued together. There are various ways to join wood but woodworking glue is usually strong enough. Biscuits do not add much strength but they are good for alignment.
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