T+G or Not T+G

[Gere Flewelling]

I need advice from woodworkers with more experience than mine. Actually that is most everyone.  I am looking to glue up some hardwood boards to make a wide board for a furniture project I am starting on.  My question is: is it better to glue square cut boards together using dowels or is it acceptable to glue a tounge and groove joint together?  I have an old shaper that makes nice T+G joints in 3/4" boards.  I think it will take more glue than a flat joint but I am not aware if there is a reason not to due this with a glued joint.  Advice would be greatly appreciated.

[Don P]

If a joint is properly machined, nothing is needed, just 2 flat faces mated together. Anything else is more about trying to maintain alignment than enhancing the strength.

Glue joints have been know to fail, nothing wrong with plan B.

[Ianab]

T&G is usually used as an expansion joint, to allow for seasonal movement in situations where you want to use solid wood, but have cross grain connections. Like the back of a bookcase or floorboards. The T&G are not glued at all, so allow some movement. 

As long as you get the edges of the boards jointed true and get a good glue line the glue should be stronger than the wood itself. 

Having said that, some sort of mechanical connection can help with alignment as you bring the 2 boards together. T&G, spline, dowels etc. They don't add any strength but can make assembly easier. 

[Larry]

A properly made glue joint is stronger than the wood so nothing needed to add strength.  If using a jointer you joint one board with the show side against the fence and the next board with the show side away from the fence.  This corrects any alignment error in the jointer.

Their is a issue with alignment.  When clamping the glue up the boards can shift as the glue is slippery.  To help with that I've used dowels years ago.  I think they are a pain.  Easier is cauls or biscuits.  Small panels I usually use nothing.  Little bigger and I use cauls, they are just a board that I put packing tape on so the glue doesn't stick.  Than I clamp it across the panel.  Big glue ups I use biscuits.  We just did a 4' diameter table.  Six or seven boards.  Glued up three pairs without anything than glued the three pairs together with biscuits.

[firefighter ontheside]

For my glue ups I will often use biscuits just to help align large panels.  On small glue ups such as cutting boards or small tables I use just glue.  It's important to have a good fit though.  

[DWyatt]

I'll echo what everyone else said. Just glue is fine, I use biscuits for larger stuff to help me to scramble as much trying to get things to line up when the glue is wanting everything to slide. I also do exactly as Larry says, lay out the panel then joint the edges alternating. I try to glue everything up thicker and narrow enough so it can fit through the 20" planer after the glue dries. 

[Gere Flewelling]

Great advice! Thank you all for responding. I had never heard of alternating faces when using the jointer. I will definitely remember this as I proceed with my projects. Thanks again, GF

[kantuckid]

Great advice! Thank you all for responding. I had never heard of alternating faces when using the jointer. I will definitely remember this as I proceed with my projects. Thanks again, GF

Some factors are: freshly cut wood face glues better than an old cut; glue area temps need to be within the glues range of use and cure; not all glues have the same strength or assembly times-learn from mfg.'s info what's your best choice; certain woods call for certain glues that work best with oily woods like teak; The wood faces like to be truly parallel, not forced by clamping to close the joint.
Another glue up tip I use often is that wax paper resist glue so when aligning your boards you can easily use wood scraps to assist that alinement with wax paper as a go-between preventing the scraps from becoming part of the assembly.
probably the most important procedural tip is to ALWAYS! do a trial run w/o glue and using every clamp and whatever else in that trial run.
By far the most challenging glues ups are multiple piece assemblies that call for glue with increased open times.
If the woods dark I always use TitebondIII, exterior as it dries dark. I don't keep dark versions of TitebondII on hand as the exterior suffices.
The least expensive, strongest glue for most uses is TitebondII. Other brands have the same yellow glue.
Leave the white Elmer's for kids as todays other glues are far stronger-I'm old enough to remember when it began to replace hide glue. Hide glue is still a great choice for certain, specific uses.
Biscuits I've never used (personal preference IMO) and rarely I do use dowels on glue-ups.
As for furniture back panels made from boards- I like to use shiplap on something like a corner cabinet as less work to create the laps, vs T&G. Some manufactured glue-ups done under highly controlled circumstances in factories use finger joints and T&G's etc., not home shop style.
I don't normally plane after a glue up but it is a sometimes thing based on the wood pieces involved. I do use a few thicker pieces at times when the excess can be unseen in the underneath of say a chest of drawers top and no reason to plane it when sanding works OK. 

[Don P]

That is a good point, machine and glue that day. When I worked on a wood panel gluing line we would shrink wrap the pallets that were between the straight line saw and glue machine each night to try to keep the joints "freshly machined".

One that has gotten me multiple times is temperature. It isn't the air temp in the shop or jobsite that matters, it is the ice cube temp of the stick of wood that ruins the glue up.

Our coffeetree coffeetable was a drying experiment gone wrong. The thick, wide boards were apparently not as uniformly dry as I thought. Drying wood is stronger than glue or wood. Be at the moisture content the piece will see in use.

[metalspinner]

Patience has always paid off for me. I try not to glue more than one joint at a time. And I don't like biscuits or dowels. Instead, I use small clamps at the ends of the boards faces. This keeps those faces flat to each other and helps alignment of the rest of the board. 
Parallel clamps really make glue ups easy. Make sure your bench is flat and have a dead low mallet handy just in case one of the boards bows up on you. Glue is slippery!
Oh, and starting with thicker stock and sending those glue ups through the planer hides lots of sins!