Thread: Large slab table - support advice

A quick drawing is going to make things easier.

It sounds like a Yes, you need more support .

Were all probably just guessing a bit at that description though .

Rob

Welcome to the forum.

we are nosey little sods we love to see drawings or pictures...gives us our jollies.

Table plan.jpgTable1.jpgTable2.jpgTable3.jpg

I'm just adding a second sketch to which I've added the cross-brace for the legs..
Table plan2.jpg

My main thing is, are there any rule's of thumb for this sort of stuff when it comes to supporting braces, or spines? I've seen tables in shops where some do and some don't, so it's a bit confusing for a first time table builder (yes, I know this is a big mother for a first time table'r, but, go big or go home, hey!)

The guys I got the wood off was pretty convinced that for this thickness it wouldn't be necessary, even when I told him I was going to put a spine in. I figure that he's been making these for years so he's gotta know what he's talking about, right? Plus, I'm also of the opinion that if a 150kg+ table top wants to move in a year or two, then a spine is not going to stop it.

Thanks for your time and I hope the drawings and pics are useful!

First drawing looks pretty good . I don’t think you need the stretcher which you put in the second picture .

It does depend on how your fitting the two legs to the top . Steel top plates 10mm thick well screwed into the legs with well placed holes around the outside to screw the leg top plate to the top would be good . You can get some mighty good screws these days too . Get that right and all that can happen is the top could sag a little . You’d probably only see it if you get down one end and line your eye up with it . I wouldn’t be doing those top plates out of wood .

I was shown some amazing screws yesterday . I’ll get a pic and show .

Rob

A supporting frame? No. When it sags, it shouldn't be by much. Probably little more than it would with a frame, given the weight of the top and that a frame works by sagging until it's at sufficient tension.

Personally I'd stick with the stretcher idea...

1. They look good.

2. If you wedge the stretcher ends it's a simple matter of giving 'em a few taps any time the table even seems to have a loose joint.

3. Depending how the legs are fixed to the top, it can make for a quick and easy breakdown & reassembly. Always a bonus with heavier furniture.

4. A trestle table is significantly more robust than one without a stretcher... particularly in scenarios where a heavy table is dragged along the ground for any distance, even just a few cm.

A table of that size and made from a heavy specie requires a bit of thought re assembly and reassembly. The stretcher is a good idea as it allows the legs to be assembled and stood ready to receive the top. On breakdown you would have two legs one stretcher two wedges and the top. A total of six components. All pieces can be sanded and polished individually. All pieces can be carried individually to negotiate difficult site. All pieces can be assembled and taken apart as and when required.
If the table is made as a monolithic structure it will require far more effort and people to shift it.

I mentioned screws before .

These screws are around 10mm maybe 12mm wide on the thread . Didn’t measure but I can later . Not sure where you get them or what type they are .

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Rob

Originally Posted by auscab

First drawing looks pretty good . I don’t think you need the stretcher which you put in the second picture .

It does depend on how your fitting the two legs to the top . Steel top plates 10mm thick well screwed into the legs with well placed holes around the outside to screw the leg top plate to the top would be good .

I'd also go with steel strap top plates but I don't think a 10mm thickness is required, as 6mm or even 5mm would be more than enough.

Thinner strap could even be recessed into the underside of the table and covered with a thin decorative timber strip that would hide the top plate completely.

Stainless steel buffed to a matt finish would also worth be considering as the top plate material it won't be readily seen and it will not rust.

Why would you propose steel plates over a jarrah one?
I've been chatting with my father-in-law, who was a carpenter, and we've decided that we'll put a supporting brace (block/triangle) between the underside of the table top and the inside of the legs. This should provide support in case there is any undue longitudinal stress placed on the table to stop it from collapsing. This will be in addition to the stretcher between the legs.

I do wooden top plates mostly but never under 90mm thick.
I was looking at your idea at first thinking your going for a clean modern minimal look . If your getting away from traditional design like you are . Then steel has some good advantages over wood design wise and extremely better engineering possibilities strength wise . Sure , 4 or 5 mm plate will do the job but Id give it some extra grunt and go 8 or 10mm and get better screws than standard . Then you could go minimal and be very strong . No triangular braces needed . No stretcher needed .

The stretcher holding the base up ready to take the top is right . Its safe . Done right , going through with a wedge each end it will hold it .

Triangular braces sounds like something an old carpenter would say to do . They have a reputation for stuffing up good furniture design that goes way back hundreds of years .

Steel top plates wide enough , wider than the 50mm top of the base , at 150mm , will brace the top down its length if well fitted. Steel top plates longer than your 700 mm base , say 980 long , when screwed well will resist the top lifting or cupping .

I wouldn't rout and sit it in flush under the top because your taking away from screwing power. Or screwing length . No one sees it anyway unless their on their hands and knees. If you did rout it in you need 20 to 25 extra space for top shrinkage each side . The top can shrink in and stop on the steel!! I did one in steel routed in with about 10mm each side space and the top shrank the in the 20mm and had a 5mm split in the middle . It was perfect kiln dried 50mm Oak. Some people run their heating full bore all winter and pay $4000 a 1/4 for gas bills heating the whole mansion . Your table though so you have a better idea of your space and use. And dry Jarrah is pretty stable I think . I had to pick up my damaged table and take top of for repair . Lady Paid for it .

Rob

Cheers for the feedback, Auscab.

Just so I get it through my noob head, you're saying that another option would be to use a steel plate as the fixing of the leg to the base of the table top. This steel plate would be approx 10mm thick, say 150mm wide and 950 long, effectively spanning the width of the table. The plate would be fixed to the legs from the top using a number of screws, say 4 or so, through the top of the plate into the guts of the leg. These screws would be quite long and hard, possibly similar to the ones you showed in a previous photo. Then, the plate would be fixed to the underside of the table top by, let's say, 10 bolts or screws, 5 evenly placed on each side of the plate. These can only be about 35-40mm long though - at maximum.

Does that sound like what you had in mind?

The weak point there would be the 4 screws holding the plate to the legs, if my engineering memory is correct. You wouldn't be worried about the shear forces that may be placed upon the table and unsettle these hold-fasts? The table top weighs about 150kg, so I'm just concerned about the inertia and shear forces that will be placed on these screws.

I'm not trying to diss your idea here, I'm just trying to get it through my head and remove doubt.

Thanks for the feedback!