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Thread: Joinery for Square Legs and Slab Table Support? Pic inside

  1. #16
    Join Date
    Aug 2010
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    Quote Originally Posted by Gene Davis View Post
    Don't overthink this. You have the photo, and you can just work with that. Your legs are best done as a U shaped thing, no top crosspiece. Fingerjoints or dovetails at bottom, your choice. Put button feet under so you can deal with a little bit of floor uncertainty.

    For maximum moment strength against bending (i.e. racking) consider thru-socketing the legs to the table top. Thru-tenons with wedges would look like a nice feature, one that you are proud to display.

    Here's a quick workup I did in Sketchup. Leg members are 1 x 3 in section.

    Thru-tenon legs have been done for centuries for milking stools, so don't pay attention to those who say someone will sit on your table and wreck it unless you build it like the Hoover Dam.
    Sorry about being late to the discussion, but, this idea, I'm not so sure you don't need the top crosspiece in which case the tenons into the top wouldn't be needed. I would worry about not having the support under the table going across and I would also worry about seasonal growth and shrinkage concerns of the top with the tenon into the top as shown. Not saying it won't work, just that there are some issues to be thought through with this.

  2. #17
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    I suggested that the top crosspiece is not needed and that the way I show in my Sketchup model is best.

    It is best if the slab is thick, like most all are when doing this current vogue of live-edged sawn wood slab work. A through-tenon in two inches of wood, nicely fitted and wedged, provides 360 degree moment strength far superior to any type of corner joinery if a four sided thing is done to emulate the welded steel tubing.

    It only works, though, if the slab is either well stabilized and solid, or stiffened in some way with battens on the underside. The photo the OP showed has the slab top as two pieces, and maybe just butted and not joined. The steel-tube box-leg stand is perfect for that design, because the top member of the tube-boxes joins and supports the two-piece top.

    One can get acceptable joint strength in a wood box that emulates the steel tube leg subassembly, but to get enough surface area for glue to get the moment resistance wanted, one might end up with a chunkier look than with 1 x 2-1/2 steel.

    That is why I suggested the arrangement I show in my Sketchup model. I would do this with a bookmatched top, jointed well and glued at center, with the bowtie dutchmans for decor.

    George Nakashima would do the bookmatched top, edge jointed well, but the slabs separated with a 3mm reveal, and the bowties would be all the way through. He would have battens underneath, likely fitted with dovetail slides, and the joinery concealed. George is dead, but his designs live on.

  3. #18
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    To avoid battens I would take a guess and say that the top would have to be fairly heavy and also made from straight grained 1/4 sawn material.

    The wider the piece is, and the more interesting the grain, the more I would expect some heavy battening would be needed.

    This base idea is not ideal for this type of bench, it was originally designed by George Nelson, in wood, for a slated wooden bench and works because the bench top is slatted (wood movement is not a concern in that case). I think your best approach would be to research base styles which will function properly with a solid wood top that is going to have seasonal movement.
    Bumbling forward into the unknown.

  4. #19
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    Schwarz just came out with a book "The Anarchists Design Book" on two simple ways to make home furniture. One method, staked legs, works much better than most people think it will. The method uses relatively small, usually oak or maple, legs with tapered tenons on the end, placed in tapered through mortises, in thick, softer wood tops, pine, poplar, elm... The tenons are typically wedged into the top and sawn off level. Many chairs, benches, tables have been made with this method dating back to Egyptian furniture makers. Even without rungs, chairs with four or even three legs hold the weight of human bodies, sometimes for centuries. I have a small saw bench with staked legs made in a Schwarz class that I sit, stand on, and saw on regularly. The beauty of this joint is the weight on the top simply tightens the joint. There are much more elaborate mortise & tenon designs than simple staked/ tapered legs, but the simple tapered round joint works very well.

  5. I agree with most here that, from weakest to strongest and best resistance to front to back racking would be 1. Lock-mitre 2. Box joint 3. Dovetail. While I would never discourage someone for over-building, I think for a coffee table, which is usually squat and sits low to the ground, a lock-mitre joint wouldn't be the worst thing in the world....
    Stretchers will help with side to side racking and I don't think they'd look bad either...
    As for how the base is attached to the slab, I would definitely consider using slotted holes in the base to screw through with pan heads and washers to allow for wood movement in the top. If you run a stretcher along the center of the underside of the top, fixed screws along that length will be fine.

  6. #21
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    The joint of the verts to the floor piece are the ones that concern me. That racking thing is real and sooner or later those joints will fail.
    Perhaps if the bottom (floor piece) was set vertically and connected to the vertical pieces (oriented to the table edge as you show it) using a pinned bridle joint (3 heavy pins per joint, with glue of course) you could save this basic concept. I know I have suggested a change of the design but... In fact I would run the floor pieces past the legs a bit - 3/8" to 1/2" and make them taller than the legs are wide. Just another way of thinking.
    "... for when we become in heart completely poor, we at once are the treasurers & disbursers of enormous riches."
    WQJudge

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