Drilling into the edge of plywood

Question

I want to make a little wooden construction to house a bird inside during winter for a few days when it gets too cold outside.

I want to be able to take it apart quickly so it doesn't take up much space.

I was thinking of using dowels to keep a few plywood panels together. No glue, no frame, no nails or screws.

To do this I would have to drill into the edge of plywood to fit in the dowels. Now I've heard people say you shouldn't drill into the edge of plywood, because the glue would loosen and the fibre sheets would come apart. I've seen the sheets of plywood come apart due to moisture and wood rot, but does it really happen by just drilling into it? Should I avoid drilling into the edge of plywood to put in some dowels? Thank you.

Answer 1

If you aren't locked into the dowel joints you've described, consider to make the build with a variation of the tab and slot assembly, but increase the tab and add a slot in the tab as well for a wedge:

The original source of the above image describes it as a loose wedge joint and is constructed in the images from solid plank lumber, but I don't think that's a requirement for your project.

You would have to cut slots to pass the tabs through and ensure accurate dimension placement, but I think it would be quite workable.

My search for tab and slot returned a reference that doll houses use this method because the plywood is thin and can't be easily joined using other methods. No reference was made to the ease of disassembly, but that's fairly clear. Tap the wedges out in the opposite direction and you have a flat-pack ready to go into the box.

If your plywood is thick enough for wood dowels as part of the joint, you could combine the tab and slot and add a couple of dowels for additional strength. Overall you could get away without glue in any of the joints.

You'll need a good drill bit, the diameter of which should be the thickness of the plywood, a sharp chisel and mallet and a hand saw or coping saw to cut the tabs.

Answer 2

You can drill into the edges of plywood. Screwing into the edges isn't great, especially if you don't pre-drill, because the screws can easily push the laminations apart. Holes for dowels wouldn't be so bad. An even better method would be to use some knock-down connectors such as these cross dowel nuts -- basically, you drill a hole into the edge of the plywood, and an intersecting hole through the face. Insert a nut in the intersecting hole, and then a bolt into the edge hole, and you'll get a strong connection that's easy to take apart.

Answer 3

I was thinking of using dowels to keep a few plywood panels together. No glue, no frame, no nails or screws.

That would work.

Dowels
Having taken apart some dowelled furniture which was unglued or too-lightly glued in the factory this is definitely a viable method of construction even for certain furniture items, so should be perfectly adequate for what you plan to make.

Automatic perfect alignment can be guaranteed if you use through-dowels rather than the more common method of drilling two separate holes so the dowels remain hidden.

Screws instead?
The basic methodology is the same, but screws would make disassembly and reassembly much easier (once you unscrew the thing falls apart by itself).

Screwing works best with carefully chosen screw types¹ but can be done with virtually any screw if required². You need to pre-drill clearance and pilot holes holes for the screws naturally, in addition to doing a countersink or counterbore for the screw head to sit into. Note: there are drill bits available which will do all three in a single operation, but doing this infrequently the multiple drilling operations aren't too tedious and saves having to buy a set of bits you may seldom use.

Now I've heard people say you shouldn't drill into the edge of plywood, because the glue would loosen and the fibre sheets would come apart.

Well if anyone says that without providing any additional info you might want to stop listening to anything else they say. The details matter, hugely. Not only can you drill into the edge of plywood but doing so has been standard practice for roughly 70 or 80 years!!³

but does it really happen by just drilling into it?

It can, yes.

Should I avoid drilling into the edge of plywood to put in some dowels?

As you expect by this point, nah! But there are some caveats. The quality of the ply is important (this is one of the bits of additional info that matter) as is the size of the hole in relation to the thickness of the plywood...... it should be obvious that there's little risk in drilling a skinny hole into thick material.

For larger holes, while you can do it with standard drill bits (twist bits) you'll often find that lip-and-spur / brad-point bits are the better choice.

Particularly where the holes will be quite large in relation to the plywood thickness (1/3 or larger), and also when using twist bits which have more of a wedging action, it's a good safety measure to firmly clamp the plywood at each hole location as you're drilling, or, clamp battens along the edge so you can drill an entire line in one go without having to reposition any clamps.

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¹ Such as Confirmat screws.

² Although with basic screws if the requirement is to take the thing apart many times over the expected lifespan reinforcing the pilot holes would be advisable. This can easily be done by dribbling some glue into them. If using epoxy or superglue don't reinsert the screws until the glue has set unless you've waxed them thoroughly!

³ For two of the primary joining methods in plywood construction — glueing and screwing, and glueing and dowels.

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Edit: I'd forgotten this Answer from 2016 but it covers a lot of the issues, What length screw should I use for a computer desk