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Randy
Joining large timbers for table top

Hi, Looking for advice. I have some large 4"x 8 " x 7' hem fir timbers that I plan to make into a table top. I am looking for advice on joining them. I have a biscuit joiner that I have used for thinner stock but feel something else may be needed. I was thinking of routing a joint and using strips of plywood and glue.

Any advice appreciated.

ed21
Re: Joining large timbers for table top

I believe the biscuits are mainly for aligning the boards for gluing and clamping. The glue is what holds the boards together.

JLMCDANIEL
Re: Joining large timbers for table top

If you are leaving the planks 4" thick you should only need glue. That is a very large glue surface.

Jack

Re: Joining large timbers for table top

Really? I have trouble wrapping my head around just using glue. Not that I want to add any weight to the project:) or make it more difficult.

Thanks for the reply.

Seth
Re: Joining large timbers for table top

I've made a table with 1x8s that I glued on the side and used biscuits. I don't know if the biscuits provide any strength, but there is no way I could have gotten all those boards aligned without them.

As for 4x8s, those sounds pretty substantial. It would almost be a shame to join them with something as common as glue. It would be a lot more work, but I would look into carving them and joining them like old post and beam joints, perhaps with hand-hewn pegs. Maybe even label the joints with chiseled roman numerals... Note: all of my "quick projects" end up taking months or years, so take my ideas with a big grain of salt.

ed21
Re: Joining large timbers for table top

A table built with 4x8's is going to be real heavy. Just saying.
My clamping skill aren't very evolved, but without biscuits or some sort of rout and spline, the boards tend to move as they are clamped.
BTW- glulam beams rely only on glue. different than what you would use though.

A. Spruce
Re: Joining large timbers for table top

Titebond II should suffice, however, you're going to have to make sure that your mating faces are absolutely straight and true and do NOT skimp on the clamps! If this were my project, I'd clamp from both sides (top and bottom ) to assure even clamping pressure, completely closed joints, and an overall flat surface when completed.

One last tidbit of info, wood glue works by binding wood grain together, the glue, in and of itself, is very weak, that is to say, pour glue into a gap, all you've done is fill a gap, there will be no strength, put two pieces of wood tightly together with a bit of glue and you've got a joint that is going to hold.

Re: Joining large timbers for table top

Really great advice. Thanks to all.

When it is finished.. probably late spring I will follow up with a photo.

JLMCDANIEL
Re: Joining large timbers for table top

One other thing, if the planks are not quarter sawn alternate the growth rings, that is one with growth rings up next with growth rings down for a more stable unit.

Jack

Sombreuil_mongrel
Re: Joining large timbers for table top

It is a large undertaking to make a giant glued-up panel and make it planar and keep it so.
How are you going to dress it after the glue dries? A 4ft planer or thickness sander is almost unheard-of, doing it by hand is a very skilled operation, not doing it at all will leave no room to correct things after the fact, makes the material prep a machining job worthy of NASA.
If you're making a rough-sawn industrial-looking top out of used lumber with the as-found finish, I recommend bolting it through with all-thread like a butcherblock and forgoing the glue. Use a few dowels to keep it aligned every foot or two, let the bolts do the fastening work, adjust the warp with shims between the timbers. Place the worst boards at the edges, the truest ones in the middle.
Casey

Mastercarpentry
Re: Joining large timbers for table top

If you're not putting this on a solid concrete slab you're inviting problems because it might end up weighing a ton- literally- and the floor has to hold this and everything else on it too. And the leg structure will have to be appropriate for that weight as well.

I'd find a sawmill and have them resaw to half the thickness, still plenty of strength left, half the weight, and twice the lumber to work with. Edge truing can be done there too. If you want a smooth surface have them plane the boards after sawing and truing. Then biscuits and glue should be enough with good clamping and good fit. Glue and pocket screws from underneath can work well too.

Wish I had that material to work with so make the best of it!
Phil

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