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I am building a small wooden box. To ensure the joints are strong, and to compensate for variations in my cutting, I was planning on using through dowels to get a good strong joint. I was also hoping it would be a bit of an aesthetic feature too.

Following the usual rule of thumb, the 6mm thick wood suggests 2-3mm dowels are as large as I should go (this is about 1/16 inch). But wood glue is pretty thick and gloopy (viscous), so how would I be sure to get good glue coverage. I can't pour the glue down the hole (it won't go in the small hole).

I was planning on coating the dowel and pushing it in, hoping that would give coverage down the full length of the dowel. Perhaps someone could tell me how it is supposed to be done?

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Following the usual rule of thumb, the 6mm thick wood suggests 2-3mm dowels are as large as I should go (this is about 1/16 inch).

3mm is maybe pushing it (as it leaves only a quarter of the wood's thickness to either side of the drilled hole) but on the other hand 2mm dowelling would be really skinny, towards the low end of what's really practical in a lot of woods — could be excessively prone to breakage both during manufacture and usage.

If you're comfortable using 3mm I wanted to mention that you can use bamboo skewers. These are especially strong, and from the sets I've bought typical diameter seems to be in the range of 2.8-3.1mm. Because of the sometimes sloppy fit in a 3mm drilled hole I would advise switching adhesives and using epoxy because PVA has almost no gap-filling ability.

1/16" is 1.58mm BTW. 5/64" is a closer approximation to 2mm (only 0.02mm off), and although this probably seems an awkward fraction to a metric thinker it actually appears to be a commonly available bit size.

But wood glue is pretty thick and gloopy (viscous), so how would I be sure to get good glue coverage.

You'd use a suitable glue applicator, same as when applying glue to any recess where you want fairly uniform glue coverage.

I was planning on coating the dowel and pushing it in, hoping that would give coverage down the full length of the dowel.

Honestly, for these that's likely to be perfectly adequate. After all, some woodworkers only apply glue to one side of almost every joint!

It would be best practice to add glue to both the hole and to the thing going in the hole (just as it is in mortise-and-tenon joinery) but I have seen other people barely glue theirs in. And it's worth mentioning that in some applications wooden pins/pegs (typically sharpened to some kind of point) are used like nails and aren't glued at all.

However I like to be as conscientious as possible and glue mine in, because, why not?

BTW if you want to maximise the reinforcement pins provide, don't put them all in perpendicular to the surface. A slight angle on some or all — e.g. like this / \ or this \ | / gives a dovetail-like hold, which gives a noticeable bump in strength. As I mention in a previous Answer or two, the angle only needs to be shallow for the effect to kick in, so the ends aren't very obviously oval in case that would bother you.

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    All spot on. I would add that an alternative to very thin dowels is to use carbon fiber rods glued in with thin epoxy. The rods are readily available and inexpensive in both 1mm and 2mm diameters, and cut easily. Epoxy bonds well to the rods (which of course are really carbon fibers cemented together with epoxy).
    – Walnut Close
    Commented Jul 4, 2022 at 20:15
  • @WalnutClose, TVM. I always forget about carbon-fibre rods, although I've seen them used as reinforcement in a few projects. I believe they're nearly unbreakable, but purely in terms of looks being jet black they can be visually striking.
    – Graphus
    Commented Jul 4, 2022 at 22:02
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    @Puffafish, from everything I've seen and read they sand well. The dust is charcoal grey/black of course, and presumably acts the same as any fine dark dust so the usual precautions have to be taken especially if the project wood is light in colour (same as with a project made from walnut and maple, contamination of the maple with walnut dust is always something something you have to watch out for because it makes the maple look dingy). But anyway, you really don't need the enormous strength of carbon-fibre rods here which is why I didn't update the Answer to incorporate them. [contd]
    – Graphus
    Commented Jul 5, 2022 at 11:16
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    The strength added by hardwood or bamboo dowels is considerable, and in a project made from strong ply or hardwood a few narrow pegs can change something that might break if stressed badly or the piece is dropped into something almost unbreakable.
    – Graphus
    Commented Jul 5, 2022 at 11:20
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    @Puffafish (Are carbon fiber rods going to sand down nicely? I've never tried them, but they're very different to wood, so I'm not sure how they'd smooth down.) They sand just fine, but I strongly recommend that if you use them, you finish the wooden surfaces of the box with at least a primer or sealer coat, and preferable all but the final coat, before you place the dowels. As #Grraphus says, the carbon fiber sanding dust is dark and will work its way into unsealed wood.
    – Walnut Close
    Commented Jul 5, 2022 at 15:58
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Consider to score a spiral along the length of the dowel, or scribe lines parallel to the length (fluted dowels). This is akin to some commercially available dowels with rather large scores, providing additional surface area on which the glue will bond. Images from linked site.

fluted and spiral dowel

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  • US born, native English speaker for more than 60 years. According to much research via the internet, both forms are correct. No need to correct something that is incorrect based on inaccurate information. Please take it as a learning opportunity.
    – fred_dot_u
    Commented Jul 5, 2022 at 17:59
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    My sincerest apologies. Not conjugating verbs seems to be a more recent thing and always sounds awkward to me. Raised by an English major mother who always insisted on proper grammar. I'll make a note and do my best to not correct little things like this in the future.
    – FreeMan
    Commented Jul 5, 2022 at 18:03
  • This English language is such a difficult thing. I'm surprised citizens of other countries are able to speak so fluently in English. I've had my previously incorrect grammar corrected by a German national, which is humbling. So, like, you know...
    – fred_dot_u
    Commented Jul 5, 2022 at 18:35
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    Fred, no offence but please take this as a learning opportunity yourself — this is something you might want to ask about on one of the English SEs, where I fully expect multiple respondents will say that this not just less correct but in fact not grammatical full stop. To my ear this only works in a very different sentence "Consider [that] to score a spiral along the length of the dowel [would have the following benefit]".
    – Graphus
    Commented Jul 5, 2022 at 19:01
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But wood glue is pretty thick and gloopy (viscous), so how would I be sure to get good glue coverage.

Consider using thinner glue. Cyanoacrylate (CA) glue (aka superglue) is available in low viscosity versions that are great for seeping into tight spaces. The thinnest stuff will be pulled into the joint via capillary action. Insert the dowels into the holes in the bottom part, add a few drops of thin CA around the dowels and along the rest of the joint, add the top part and another drop or two of CA at the dowels, and spray with activator.

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