Glue is pretty darn strong. But for flooring or something they usually use more than just that. Biscuits help but don't add a ton of strength in that application. For a benchtop or table I would say glue is plenty.
I've joined 2X6 lumber lengthwise by making a dado with a slotting bit in my router and inserting a 1/4" spline made of BB, since it has so many layers. I'm not sure if you could keep the 2X12 lumber's eventual twisting under control that way, though. Again, what is the end use?
Hey guys, thanks for the responses. But even more so, i want to offer an apology. I promise, I know how to forum. I know it's customary when joining a forum to start with an introductory post, maybe a few helpful comments on other posts as well and then easing into my own questions. Unfortunately, i didn't have time to be very detailed this afternoon when I signed up and, to be honest, I'm not sure i have much to offer in the way of help to others. I'm mostly here to learn.
The boards I'm joining will be a farmhouse table top. I've already built one because, well, Pinterest said I could. I really learned a lot and pushed myself to learn and do things that I've only ever seen others do. Virtually the whole of the internet says to buy the Kreg jig and use pocket holes, but i wasn't sure that was going to be strong enough. I wanted my top to be one solid piece that i would later put legs on. So I bought a table saw and a dado blade with the intention of using tongue and groove, but it didn't work out so well so I switched gears and went with dowels. I like the concept but lacking proper experience and technique I really had to work to get it done.
All that being said, I'd like to build another (I'm a glutton for punishment). Should I try to perfect the tongue and groove, work out the kinks with the dowels or go with the biscuit joiner I've been given (all methods will still involve a ton of glue)?
Anyway, sorry for the length but maybe it will help you to see where I'm coming from.
You really don't need to use t/g, dowels or screws to assemble the main boards in your tabletop. Edge gluing with good modern glue will be quite strong enough as long as you properly prepare (joint) the edges of the boards to get a good joint.
If you plan to have breadboard ends, you need to use mortise and tendon joint and do NOT glue the breadboard, instead use either screws or dowels to pin the tendon in the mortise, be sure to elongate all the screw holes except the center one to allow movement of the wood as the top expands and contracts during changes in humidity in the environment.
I did something similar for a 12' shelf that sits on top of my wall cabinets. I jointed the edges of two 12' 2×6's and then simply glued them together. I considered putting dowels through them to add strength, but I decided it wasn't worth the hassle. It has been holding some of my scrap lumber for a few weeks now and feels plenty strong.
Dowels add strength but I primarily use them for alignment. My first choice would be to go with dowels.
A 12' - 2"x12" is a big piece of lumber to run over a dado blade on a table saw. Even with a helping hand and a couple of stock supports that is a pretty unruly operation.
If I were going to try to tongue and grove a 2"x12" of that length I would use a router. Much easier to move a hand held router over the edge of the board than to try to move the board over a dado blade in a saw.
Are you prepping the edges of the 2"x12"s to square up the corners? Are you running them over a jointer?
Great question, and, it's fine to come here to learn, you'll find it a friendly place!
As mentioned above, a straight glue joint is sufficient for this application, providing your timber is jointed properly. In my projects there is a dining table made from oak which i simply glued and clamped. I was in an unusual position where I was able to leave the prepared timber in the clients house for a month or so to allow it to acclimatise. This greatly helped with movement issues.
That link that AlaskaGuy posted above is excellent, and shows well how to prepare your timber.
As others have mentioned, while dowels and biscuits help with alignment, they don't really add strength. And tongue-and-groove joints are not generally used with glue - they are used in floors and on the backs of cabinets where individual pieces of wood need to be able to expand and contract without opening up cracks.
People have been glueing up wide panels for hundreds of years with "only" glue to hold them together. Glue is stronger than even the strongest woods, and an edge-grain to edge-grain glue-up (what you're doing) is the very strongest joint in woodworking. So as long as your boards are jointed (ie straight with no gaps when you butt them up against each other) just glue will hold them together for generations. If they're not jointed straight, no amount of dowels or biscuits will do much good.
Generally I simply glue the boards up, but in a tabletop you can save yourself a fair bit of work in terms of leveling the top by using dowels or biscuits. Since you have a biscuit joiner, use that.
1. The first one is preparing the edges. Without a jointer or jointer plane, you're really in kind of a pickle here.
All I can think of is make a sled and rip an edge straight as you can with a really really good rip blade.
2. You're gonna need clamps at least every foot of table length. Alternate if using pipe clamps.
3. I'm assuming you don't have a router so running a spline is not an option (my best suggestion, btw).
You could elect to go rustic (quite the rage these days) and just don't worry about jointing or gaps, just make sure the boards are fairly straight.
I think any kind of mechanical fastener like pocket holes are a poor second choice, but it could work.
If you do pocket screws I would back them up with cross braces.
The other thing you're going to have to factor in here is wood movement. You don't say what kind of wood it is or where it came from, but if by chance it is lumber grade, it is usually too moist for furniture building. Doesn't mean you can't use it, but a 36" wide top can shrink an inch or more so if you have any fasteners in place or any cross grain gluing (like braces or slats) it can be a problem.
Cupping will also be an issue but can be reduced by looking for quarter sawn boards (vertical edge grain).
For this reason I would use 2×6's instead of 12's.
PVA glue is all that is needed, with properly jointed edges as others have said. I put a very slight hollow to the jointed edges so the ends won't split years down the road (just a few thousandths). As for alignment, don't sweat lining up the ends perfectly. Get them close, then cut the ends square to the sides when dry. Research clamping cauls (I make my own from 2×4's) for the best and easiest edge alignment and to prevent the assembly from bowing from edge clamping the boards. Any cheap clamps will clamp the edges - proper jointing doesn't require huge clamp force.
I assume the 2×12's are construction grade lumber; if so, I'd go with the picnic table look and fasten the boards to battens under the top. Remember a 12" wide board is only 11-1/4". I also would go with 2×6's.
Thanks for all the responses gentlemen, I really appreciate it! I had no idea that glue by itself would be strong enough but apparently it is! I don't have a joiner, only a table saw and hand plane (still building my tool collection) but I should be able to get it with that. I actually have my first table done but I am wanting to build another one so my questions are for that one. I'll post some pics when I get it stained. Thanks for all the help and for the warm welcome to your little community!
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