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Thread: Table design with no middle leg support

  1. #1
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    Table design with no middle leg support

    Planning on making a table using cherry that would be 30" deep with a 4" skirt and a 3/4" thick top. Planning on having a sewing machine sit in the middle of the span. How far apart can I space the legs before I have a problem with the weight of the machine cause a sag in the table? I like to be able to go 7p-1/2 to 8ft between legs, but this feels like I am asking for trouble. I could put a leg in the back in the middle of the span and brace from front to back inside the skirt, but really don't want a leg in the front between the two end legs.

    Thanks.

    Brian
    Brian

  2. #2
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    You can make a 4" thick torsion box which will not sag under that load. I have an assembly table which is basically a torsion box 4" thick by 25" by 80". I can stand on it with less than 1/32 sag.

  3. #3
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    The sagulator says an 8 foot long, 30 inch deep shelf of 3/4 cherry, with 4" high edges out of 3/4 cherry, will sag .12 in the middle with a 50lb load in the center. That would be just visible to a discerning eye.

    Actually, the sagulator only calculates for a single edge strip but you will have a front apron and a rear apron, so sag will be quite a bit less.

    If you want it stiffer, just run one or two extra stiffeners lengthwise from end apron to end apron.
    --I had my patience tested. I'm negative--

  4. #4
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    Quote Originally Posted by Jamie Buxton View Post
    You can make a 4" thick torsion box which will not sag under that load. I have an assembly table which is basically a torsion box 4" thick by 25" by 80". I can stand on it with less than 1/32 sag.
    Thanks, to heavy for me to move. Brian

  5. #5
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    Quote Originally Posted by Paul F Franklin View Post
    The sagulator says an 8 foot long, 30 inch deep shelf of 3/4 cherry, with 4" high edges out of 3/4 cherry, will sag .12 in the middle with a 50lb load in the center. That would be just visible to a discerning eye.

    Actually, the sagulator only calculates for a single edge strip but you will have a front apron and a rear apron, so sag will be quite a bit less.

    If you want it stiffer, just run one or two extra stiffeners lengthwise from end apron to end apron.
    Paul, thanks. Would I need to tie the extra skirt into the leg or just secure it to the skirt that is tied into the leg? I could use a 1-1/2" glue up and notch the leg 3" and let it sit on the top of the legs with 1" in a slot or domino it in. Brian

  6. #6
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    Quote Originally Posted by Brian Runau View Post
    Paul, thanks. Would I need to tie the extra skirt into the leg or just secure it to the skirt that is tied into the leg? I could use a 1-1/2" glue up and notch the leg 3" and let it sit on the top of the legs with 1" in a slot or domino it in. Brian
    I'd run it from the left apron to the right apron, centered front to back. Fasten it to the top however you were planning to fasten the top to the aprons, z clips, figure 8 clips, whatever. Dominoes into the side aprons would work fine.
    --I had my patience tested. I'm negative--

  7. #7
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    Quote Originally Posted by Paul F Franklin View Post
    I'd run it from the left apron to the right apron, centered front to back. Fasten it to the top however you were planning to fasten the top to the aprons, z clips, figure 8 clips, whatever. Dominoes into the side aprons would work fine.
    Thanks for the input. Brian

  8. #8
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    Quote Originally Posted by Brian Runau View Post
    Thanks, to heavy for me to move. Brian
    A big feature of a torsion box is that it is light. That’s why they build airplane wings like torsion boxes. You can make one to the dimensions you’re talking, and make it weigh less than 40 pounds.

  9. #9
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    If the table is primarily to hold the sewing machine, consider making a torsion box top with a recess for the machine so the table top is at the height of the feed into the machine. I have done this and it makes for much smoother sewing. A downside is that you can't easily wrap a tube like a sleeve about tne end of the machine unless you lift it up. Not a problem with quliting or sailmaking, but could be with clothes. You'd also want to make an insert to fill the recess when the machine isn't there. The recess needn't be a close fit.

    Whatever you do, make sure fabric can slide smoothly over the edges and corners without snagging.

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