Home Improvement Stack Exchange is a question and answer site for contractors and serious DIYers. It only takes a minute to sign up.
Sign up to join this community
Let me start off by saying I have some basic knowledge of tools (basic home repairs and patch jobs), but no experience with "actual" woodworking projects. For my first project I wanted to try and build a simple serving tray. Similar to this one.
My question is, where the corners meet, will wood glue be strong enough to hold the sides together? Or do I need nails or screws? Since I'm new to woodworking I'm not exactly sure how much holding power to expect from wood glue.
Better wood glues make the claim that your joint will be stronger than the wood itself. That's to be taken with a grain of salt, as it really depends on the application. It's often true that a broken joint actually breaks off a layer of the wood rather than the glue itself.
In this case, if you glue the joint thoroughly I'd expect it to perform as expected, though the thickness of the side rails (and therefore the joint surface area) is a factor in ultimate strength. Unless the tray was dropped or otherwise impacted it will probably hold up well. That said, it might be wise to run a single small finish nail (with or without its head) through the joint to reinforce it. If you're going to stain it dark it's easy to hide something like that.
My Dad's shop teacher always said:
The nail holds the joint together while the glue dries.
If you clamp it tightly while it is drying, it should be fine. Those tiny little nails don't really offer much holding power.
If you use a better joint than a miter or butt joint, something with increased surface area like a dovetail joint, a nail is even less necessary.
Wood glue works best when you join two pieces of wood along the long-grain. It helps to make the joint close fitting and to clamp the joint together while the glue dries. In that case the glued joint can be expected to be stronger than the wood itself.
If you make joints using end-grain they are usually much weaker.
In your example it looks like the mitred corner joints are reinforced by splines. This is where a slot is cut across the corner, a piece of thin wood is then glued into the slot. This makes for more of a long-grain to long-grain joint.
As Jon noted in his answer, nails and screws are mainly used to hold the joint together while the glue dries - when you don't have suitable clamps.
Note that there is a woodworking.stackexchange.com where you can get very good answers to these sorts of questions - well worth browsing some of the answers there.
The main concern is that the sides (especially the sides with the finger slots) remain firmly attach to the bottom. Those are the most important joints, by far. You might want to predrill and screw the bottom to the side pieces.
Whether the four sides remain tightly joined is of looks. The photo shows splined mitre joints. The mitred joint alone is not going to hold up with just glue because it means gluing endgrain to endgrain. Additionally, a mitre joint is only precise at one humidity level. Increase the humidity and the wood swells, causing the joint to no longer be a pair of 45 deg bevels. Same with lower humidity. This will even more stress on the mitered joint. The important aspect is the splines. You will need a good fit between the kerf and the spline, not too tight and not loose. glue up the 4 mitres and let dry, then cut the 4 kerfs, then cut splines to match the kerf, keep cutting/trimming the splines until there is a snug fit. Don't do it the opposite way by recut the kerfs to match the splines. If all else fails, use a loose spline and some glue that is designed to fill gaps. It is this glue joint that will hold the mitres together through seasonal changes in humidity.
