Round table from one big plank - how big?

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So I've got one big plank of walnut out of which I'd like to make a round table. I've determined that since the plank is 12x96 I have 1152 square inches of area, which equates to just over a 38" diameter table, (ignoring the realities of loss due to saw kerfs and the aesthetics of infinitely narrow strips.) Now assume that I rip the plank into 3 strips of 4" - what's the biggest diameter I can get? Is there any sort of formula I can use to see what my options are? Thanks.
JP
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Hey JP, (left arm is in a cast following surgery. all typing from this point will be lower case) i don't follow your reasoning very well. how thick is it? why not cross cut it to 32 long, rip and edge joint tp 11 wide each, and edge glue. you'd have a 33x32 plank which would produce an almost 32 inch diameter table. the waste would be minimal compared to making the strips you refered to and cross cutting and gluing stuff up. marc( who still managed to turn a cocobolo pen tonight- post surgery- to give to his doctor tomorrow when he removes the drain from my arm. that cast had my left arm set at the perfect angle for holding the cutting tools. what's that saying? " when life hands you lemons, make pens". well, something along those lines anyway.)
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Sorry, but that's incorrect. The waste from this method would in fact be a very large fraction of the total. He's starting with, as he noted, 1152 square inches; a circle with a diameter of 32 inches has an area of only 804 square inches, so the waste is 348 sq in or a bit over 30%. That's not "minimal" by any reasonable definition.
Ripping into 4" strips (actually about 3-7/8 after kerfs and edge jointing) wastes only 3/8" x 96" = 4 square inches. Obviously there will be more wasted than that when the strips are cut to length and glued up, but it won't be anywhere near 30%.
Jay -- I'm sure there is a formula, but it won't be simple to derive. You can get an approximation, though, from the following:
The largest circle theoretically possible, with zero waste, would have radius = sqrt ( 1152 / pi ) = 19.15 -- so a bit over 38" diameter is the theoretical maximum.
I think as a practical matter you're going to be limited to 36" diameter (nine strips). Best to draw it out on graph paper, I think.
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hey Doug, no argument here on the math but i'm looking at from a practical point of view. unless there is a real need or desire to get the largest diameter out of that plank i think the time and effort put in to cutting and gluing all those strips would be better used making the table with the least amount of cuts. plus, i think its appearance would be enhanced by showing the wider grain pattern of the 11 inch boards. sure, that's just my opinion/approach to this but i think it would turn out easier to construct and finish, and still be a reasonably large circle. i've made several circular side tables but none that large, twenty- two inches was the largest and i used a sliding dovetail to join the pieces. these were teak tables and i wated a glueless joint. Marc
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"marc rosen" wrote: ======================================

==================================My gut tells me that an 11-1/2" wide plank, sooner or later, is going to cup.
Lew
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On May 21, 10:44pm, snipped-for-privacy@milmac.com (Doug Miller) wrote:

I'm pretty sure I'm going to rip the plank into ~4" strips, so that will make my job easier. I'm going to play around in SketchUp, like someone mentioned, to see about exact cut-lengths. I could even try to make my cuts on an angle to help minimize waste. I wonder if the big millwork shops that make (lots of) round tables glue up and cut to minimize waste? Hmmm....
Thanks for the replies, everyone.
JP
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Jay Pique wrote:

That makes perfect sense since you will be flipping them, in order to stagger the end grain (cupping).
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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On Fri, 22 May 2009 19:04:23 -0700 (PDT), Jay Pique

I imagine there would be some of that, but there would be a point at which the increased labor cost to minimize waste would exceed the cost of material conserved. And, I'm also sure that optimum, minimum total cost point would be quite different between a hobby for fun shop and a production for profit shop.
Tom Veatch Wichita, KS USA
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Very true. Highly dependent on labor costs and costs of materials. At work I make tables from reclaimed wood, which easily tops $10/ bdft., and let me tell you that I'm not getting rich! (Monetarily, anyhoo)
JP
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wrote:

I'm pretty sure I'm going to rip the plank into ~4" strips, so that will make my job easier. I'm going to play around in SketchUp, like someone mentioned, to see about exact cut-lengths. I could even try to make my cuts on an angle to help minimize waste. I wonder if the big millwork shops that make (lots of) round tables glue up and cut to minimize waste? Hmmm....
Thanks for the replies, everyone.
I worked in a table shop for a while, we primarily made round red oak pedestal tables.
We cut all the material for the tops the same length, after glue up the tops were sanded in the square and cut to round with a bandsaw, the corners were saved to make glue ups for feet, very little material was wasted and there was no complex cutting or gluing for the tops.
There was one semi retired guy that made roll front bread boxes, shelf brackets and other widgets and gizmos out of some of the waste, most of what left as waste was sawdust and shavings.
basilisk
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(and glue up in grain-parallel fashion to make a round top)
From the point of view of minimizing waste, it might be better to rip the board into 5"-5"-2" strips, because edge joining boards will incur the most waste when a wide board is near the outer edge of the glue-up. Narrow boards at the periphery reduces that waste.
Best design results from making fewest preconceptions/early decisions.
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marc,
Have you tried turning on Sticky Keys? In the Windows Control Panel look under accessability options. (I wish I could give you more specific directions, but Microsoft insists on rearranging Control Panel with every version of Windows!)
Sticky Keys works by remembering you pressed shift or control (and maybe alt) when you press the next key. It might make typing with capitol letters a little easier.
Hope this helps,
Puckdropper
--
"The potential difference between the top and bottom of a tree is the
reason why all trees have to be grounded..." -- Bored Borg on
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hey PD, thanks for that suggestion and i will look into this, especially when i have to go back to work next week, on the other hand - no pun intended- i think if i compose most of my typings in ms word i can use their spell check and it will make most of the corrections. also i might have an easier time with keyboard placement at work. my home set up is a bit confining. Marc
On May 21, 11:30pm, Puckdropper <puckdropper(at)yahoo(dot)com> wrote:

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T
The _easy_ way to get "sticky keys" is to hold down the shift key, and do nothing else, for about 10 seconds. pop-up window, asking what you want to do appears.
Note: I find that pop-up a d*mn nuisance, but haven't found any way to _completely_ disable the functionality.
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snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) wrote:

True that.

I did! :-)
In Vista, click Start | Control Panel | Ease of Access Center | Make the keyboard easier to use
Then clear *all* of the checkboxes.
In XP, I think it's called Accessibility Options instead of Ease of Access.
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Robert Bonomi wrote:

In linux, not an issue
--
If you're going to be dumb, you better be tough

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Jay Pique wrote: =======================================> So I've got one big plank of walnut out of which I'd like to make a

================================= It's paper doll time, AKA: Graphical solution.
You are going to want to cut this 12"x96" piece into three (3) pieces that are 12" wide but of varying lengths.
The lengths will be determined by graphical layout using some graph paper and 1/4"=1" scale.
Assume you want to get a 36" finished dia. top,cut the first blank 37"-38" long.
If you joint and rip this board, you should yield three (3) pieces that are 3-1/2" wide which yields a 10-1/2" glue up.
You might get lucky and get 3-3/4" pieces, thus an 11-1/4" glue up.
The 2nd piece will be about 32"-34" determined by graphical solution. (Allow 1/2" min on each end for enough waste when trimming final blank to size.)
Rip and joint two (2) pieces say 5-1/2" to 5-3/4" each.
Place one board left, the other right of center board and glue-up.
The 3rd piece will be about 18"-20" determined by graphical solution. (Allow for enough waste when trimming final blank to size.
(The 18-20 is strictly a guess, but it is in the ball park)
Rip and joint two (2) pieces say 5-1/2" to 5-3/4" each.
Place one board left, the other right of center board.
Finally, there will be a 4th piece which will be short.
Plan this closely since you will be near the edge with a short piece and you are running out of material.
May want to rip into 2-1/2" strips and then add to glue up.
The above will allow the glue up in stages, not the hole thing at once.
When glued up an cured, head to the commercial drum sander and sand to size, then trim with a router and a circle template..
Have fun.
Lew
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I'd lay it out in SketchUp. And there is a "formula", it's called calculus. ;)
R
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Ignoring saw kerf width, the straightforward way to saw a rectangle into parts of a circle is to make a series of triangles and assemble like slices of a pie.
With that strategy, the board length is a multiple of the radius achievable, 96" board can give 32" circle table. Rip to 4", make16" lengths, cut those along the diagonal to make 4x16 right angle triangles: 14 degrees each. It takes 26 sections to make the full 360 degrees (actually a bit more), but there's some wood left, about 80" by 4", so you could lap-joint two 40" boards to make an X, put a quarter-circle of wedges in each 90 degree corner, and get (about) 36 to 37.6" of table after trimming it down.
You will learn a LOT about gluing and clamping before this table is done. Splines or biscuits are recommended. Practice on scraps.
A table saw for accurate 90 degree cutting is essential.
The related problem with 6" ripped boards is ... left as an exercise.
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Since you're going to ignore the aesthetics of infinitely narrow strips anyway ... Use your dado blade to reduce the entire board to sawdust. Make a circular form 38.25" in diameter and fill it with glue and the sawdust. Presto! 100% of the board used and no loss due to kerfs. If you're willing to go thinner you can even get a larger diameter out of it.
Art

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