Are barrel nuts strong?

Question

I'm designing/building a bunk bed for my toddler boys. Given that I am working under small constraints in their bedroom, I was thinking about using barrel nuts to piece together the two long sides with the two short sides instead of just nailing or screwing the whole thing together. That way I could build, sand, stain, etc all the pieces outside of the room and then connect the four sides via barrel nuts, simply, inside the room.

My question is: are barrel nuts safe to use for such a construction? Would they be equal to, or greater than, nails/screws in terms of strength?

I am obviously wanting to build something that is strong enough to be safe for my children, so any answers/suggestions you may have are very much appreciated. Thank you in advance.

A Sketchup file of the project

UPDATE:

This is what I am referring to as a barrel nut.

Could you be specific about what you consider a 'barrel nut', with your intended size? It's a widely used term, and can refer to some extremely weak connectors and some extremely strong connectors. — Aloysius Defenestrate, Sep 19 '16 at 01:05
Sure, I have updated the original question with more specifics. I don't have a specific size as I don't know much about them other than using them with the children's crib when I was putting that together. So any suggestions on the size would be appreciated as well. — The Duke Of Marshall שלום, Sep 19 '16 at 01:38
Thanks -- that's what I picture to be a barrel nut as well. 1/4-20 size, with a shoulder bolt (big wide head), with the barrel nut in the 2x4, should be perfectly good for strength. (With the caveat that you'd want to tighten them regularly... especially with youngsters.) — Aloysius Defenestrate, Sep 19 '16 at 01:57
Awesome! Thanks for the info. Would the use of some thread lock eliminate the need for regular tightening or dramatically decrease the frequency of tightening when used in a wooden project like this? — The Duke Of Marshall שלום, Sep 19 '16 at 02:31
I would think it wise to rotate the dowel so that the grain runs perpendicular to the inbound screw. — Automatic Slim, Dec 02 '23 at 19:52
@AutomaticSlim, the orientation of dowel would actually matter far less than one might expect. But in fact the whole idea of using a dowel to reinforce such a screw connection is based on a faulty premise, that screws into end grain are weak. They are weaker yes, but if done right they lose, on average, only a fraction of the holding power versus going into long grain and one can compensate for this easily by going larger or longer on the screw. — Graphus, Dec 03 '23 at 07:28

score 7 · Accepted Answer · edited Apr 13 '17 at 12:49

Yes barrel nuts are strong enough for this application. However, they're not your only option.

Would they be equal to, or greater than, nails/screws in terms of strength?

Like so many things it depends. To begin with the size of barrel nut you're comparing to is a variable, obviously the larger they are the stronger they are.

Nails are a good first point of comparison since screws are widely known to be stronger. But nail type and length matters (just as it does with screws) but with nails perhaps most important of all is how they're driven home. If you 'dovetail' or 'toenail' the nails in the strength of the connection is increased hugely compared to every nail being driven in at 90°.

For what you're looking to do some kind of screw-in / screw out connectors do seem the ideal choice though. And IMO no major connections in indoor furniture should be done with nails any longer, that's for rough carpentry and outdoor pieces only these days.

Since you're willing to do the drilling for the barrel nuts it's little extra effort to drill for the insertion of hardwood dowels instead, which can be used with conventional screws to provide essentially the same build, the same ability to be taken apart* and may actually prove stronger and more stable long-term:

^{Source: Fine Homebuilding. Note that where the drawing says to countersink that is actually a counterbore.}

This method is also slightly more forgiving of minor issues with alignment, if that matters!

If you decide to go ahead with barrel nuts you might consider locking them with Threadlock or something to keep them from loosening due to vibration. But how prone to working loose the bolts will be is down to how closely they're machined as much as the amount of movement or vibration in the piece.

*Threaded connections in wood can usually be used multiple times without any loss of strength.

Thanks for the post, the details, and the suggestions. I really appreciate it. — The Duke Of Marshall שלום, Sep 19 '16 at 21:20
How easy is it to undo the hardwood dowel in the event of having to disassemble the item (for transporting) etc.? — Andrei Rînea, Apr 04 '18 at 12:37
The screw should just back out of the hole exactly as it would if driven into the side grain of a board. However in this specific example the head of the screw is hidden underneath a dowel or wood plug, which presents an additional difficulty. Either can be drilled out if absolutely necessary, but if disassembly is planed from the outset it's better to leave the counterbore empty (not too ugly, the screw head is quite deep inside and tends not to be visible) or to use tight-fitting wooden buttons in place of glued-in plugs. — Graphus, Apr 04 '18 at 13:12

Are barrel nuts strong?

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