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.
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. =20 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.)
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.
marc rosen wrote in news:803a29be-fc4c-4e2c-a2fa- snipped-for-privacy@z5g2000yqn.googlegroups.com:
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.
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
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.
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....
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.
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)
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.
(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.
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.
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.
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