I'm a spline guy. I spline almost all my edge-to-edge glue-ups where appropriate. I'm beginning to wonder if it's called-for in all cases, however.
To wit : I'm making some pretty large drawers. They will be approx. 29-1/2" X 27-1/2" X 10-1/4" deep. A am using ash which will be 19/32" thick. There will be no exposed ends. I will use Tite-Bond regular. I could use Tite-Bond II if it's better for this application. The drawers will be hung on slides attached to the drawer sides.
I don't know where the splines are used. Does this box have mitered corners and they are splined? That is a gigantic drawer. One has to wonder, why so deep?
The splines would be used for edge-gluing. The boards I'm using for the drawers are not 10-1/4" wide so I'm having to glue up narrower boards (two in all panels except one, where I will have to glue up three boards to make my width) to get to my 10-1/4" drawer depth.
The splines would be used for strength not alignment. I plan to dovetail the corners using router and jig.
The splines would be used for strength not alignment.
In this case I don't think the splines are needed. If the glue alone doesn't provide enough strength (and it will) to your glue-ups, there's something wrong.
The only way a spline can increase the strength of an edge glued joint is if the joint is not properly prepared. To prepare the spline wood is removed, then the spline adds back what was removed. No net gain.
There is rarely any need to use glue other than Titebond regular for interior construction. Under interior dry conditions there is no meaningful difference in joint strength what ever glue you use. So why pay more and suffer a shorter shelf life of the glue bottle?
If you are capable of getting clean straight edges, cut with sharp knives, the glue line will be stronger than the wood outside of the glueline. If you are a good enough craftsman to cut perfectly mated splines with no space between the ends and sides of the spline, then get them sufficiently glued with no space around them, and no crumbs of sawdust end up getting into any of your joints, you are plenty capable of just preparing a simple glueline. If you don't get your splines perfect, it probably isn't as good as just gluing the two square edges.
The only time I use a spline is when I need a large solid wood panel like the large rustic doors with Z bracing to my shop where the boards are going to move back and forth, and the spline keeps the wind from blowing through. The spline is not glued in so the boards can move freely.
Life is hard enough without making it harder than it needs to be, so give it up.
Anytime you glue up boards, it's a good idea to make it longer than the final product. After the glue is fully cured, and the ends are cut off, as a matter of QC quality control its a good practice to try to break the scraps at the glueline.
The important part of edge gluing is a clean tight joint. Bill pointed out in another thread that most normal wood glues do not bridge a gap very well, they’re weakened when bridging a gap.
I think that in theory a spline improves strength, but in practice it decreases it. Unless your splines are perfectly square and the edges are also perfectly square then you’re creating a minor misalignment with the spline at the edge. One side of the joint with undoubtedly show a thicker glue line.
A tongue and groove is a better way, but in my opinion the drawers should be engineered so that the bottoms are strong enough with a plain joint. In the case of very wide drawers I’ve split them using a divider to add strength. In your case, 10” is not that wide.