My girlfriend does a great deal of sewing and painting, and had a large work table built for her by a contractor friend. It was sturdy and functional, but it had one major design flaw: it was assembled with a nail gun (and copious nails)! When it came time to move, the frame could not be dismantled without destroying it. So for a couple of years, she had the 4' by 8' top supported by an old dining table. It was not very stable, and far too low for her to work at comfortably. A year ago at Christmas, I promised her a new table base that would solve these problems.
It only took me a year (having a day job kind of got in the way), but this is what I came up with:
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It's built of well-dried Doug Fir, mostly from 2 X 12s machined down to size. The three leg sections are solid glued-up units, but everything else disassembles. The long front and back aprons have large tenons that fit into mortises on the end leg sections, and are secured with barrel nuts and allen bolts. The aprons are also bolted to the center leg sections. The stretchers are made with tapered sliding dovetail joints, which allows them to be simply pounded into place once the aprons/legs are assembled. Shelves screw onto the stretchers. In retrospect, it's way over-built, and I could have dispensed with the lower stretchers altogether, and simply used the shelving as stretchers.
The machine well (the drawer-like assembly at the front, which allows the sewing machine work surface to sit flush with the table top) comes out as a unit, and its stretcher attaches to the middle and end leg sections with sliding tapered dovetails.
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She couldn't wait to try it out, so here it is doing its job even before I could put the shelves in:
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I have a detailed SketchUp model of this, in case anyone is interested.