Nails plus glue into endgrain vs screws plus glue vs dado (for shelf)

Question

I'm building a hutch/book shelf for a small desk (2'x4'). Width of hutch is 48", depth 9.25", height about 18". Wood is nominal 1" thick "appearance boards" from a big box store, probably whitewood or clear pine. Back rail and panel might be thinner if I can find thinner boards.

This is not meant to be fine furniture. It's a project with my daughter for her "school from home" desk.

I was originally just thinking of using finish nails in the end grain connections (shelf and top). I recalled that nails aren't optimal in endgrain, but I was also planning on using wood glue, which I understand is pretty amazing these days.

It will hold school books, which do get heavy.

How important would it be to upgrade to screws? Or should I really do a dado joint (I would probably need to break out a chisel for the 10" long dados - I don't own a router nor table saw. Maybe I can justify buying a router now!)

If I do a dado, are screws then overkill?

Edit: thank you everyone! I went ahead and bought a router to make the dados and the also rounded all the edges. Those two modifications really make a plain piece much nicer! I’ll post an photo after we’re done!

Answer 1

To answer your question, without actual joinery like dovetails or dadoes, I'd recommend glue-and-screw. That is, some mechanical fastener that actually gives those butt-joints some strength. Because, while PVA glue is incredibly good, it is not at its best with all of the joint being 50% end-grain. Many joints like dove-tails, fingers, dadoes, or rabbets would offer some long-grain to long-grain surfaces to mate, which is where the best glue line will be found.

Similarly, grooves for the vertical pieces will aid in placement and glue-up, and will give you some strength against racking forces. But another benefit would be more long-grain as part of the glue-line, even though both axes would be less superior end-grain-to-long-grain.

The 1x4 or whatever in the back is there to guard against racking side-to-side, and would almost certainly need to be screwed unless you did a full or half-lap into the vertical pieces. You could get away with no mechanical fasteners if you had a nice clean half-lap, but I'd use at least two properly installed screws. This part would offer a less superior glue-joint, but its main job is to offer mechanical strength against racking, especially with a tight lap joint.

In short, if you don't want to make any joinery at all, you should use mechanical fasteners, and I'd recommend screws for simplicity and speed.

(An side on screws. Remember that it is the head of a correctly designed wood screw that gives you the strength in wood, so you want sufficient threads fully engaged into the second piece, with the top piece essentially only being clamped to the second; few threads should be actually engaged in the top piece. Think of the screw as a local clamp to ensure good glue joints.)

It also occurs to me that pine or other soft "white" wood will really want to cup and twist, and there is nothing in this construction that will dissuade this from happening. Since this is not heirloom furniture, that might be acceptable. But, accept that this may not sit perfectly flat, and may even split as the wood moves perpendicular to the grain as the seasons change and indoor spaces change in both humidity and temperature.

The alternative is to consider gluing up panels, alternating the grain to minimize cupping in the same direction. You can also buy softwood dimensioned panels so this is done for you already. I'd actually recommend buying these pre-made panels for this reason.

Answer 2

Dados would be best, since the mechanical part of the joint will carry most of the load.

If you go with butt joints and fasteners, I'd suggest pocket screws instead of either nails or screws into end grain. Pocket screws go into the face of the board instead of the end, so they should hold better. In most cases pocket screws are easier to hide, so you get a nicer looking project. The pockets can be made on the bottoms of shelves, for example, so that you normally wouldn't see them. That seems better than rows of screw heads going into shelves visible from the outside of the project. (You can always countersink the screws and plug the holes, of course.)

A starter pocket hole jig like the 310 from Kreg costs about $20. It's not hard to make your own with a block of wood and a bushing, but you'd still need to buy the stepped pocket hole bit, stop collar, and a long driver bit, so it's probably best to just by the jig (which includes all of those).

Typical PVA woodworking glue is very strong, but it's not quite as strong when you're gluing end grain. And in any case, I wouldn't want to rely on glue alone to carry the weight of a shelf full of books.