Are dovetails stronger than box joints / finger joints?


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With modern glue, are dovetail joints any stronger than box joints? I can see that, 100 years ago with hide glues, a dovetail joint would hold a drawer or chest together much more securely than a box joint. But with modern glues I'm told that a well fitted long grain to long grain joint is as strong as the wood, so it's hard to see how a dovetail joint could be significantly stronger than a box joint.

I appreciate the aesthetics of a dovetail joint, and I certainly understand choosing a joint for aesthetics, and being true to a traditional style. But let's say I was putting together some drawers or a chest, and I wanted really strong joints, but I wanted to use box joints. Would it make sense to go with dovetails just for added strength?

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I’m not experienced enough to properly answer your question. However, as I think about the two joints in question, I see that the long grain runs perpendicular to each other at the intersection of the two joints. So, they’re equal in that regard. My next thought, relative to gluing, is that they would both have multiple long grain to long grain areas of contact for the wood-glue-wood interface. The other thought is most box joints form these interfaces all the way across the width of the two joined boards, whereas dovetails don’t always repeat uniformly all the way across, so there may be less total wood-glue-wood area. Or, the tails are wide and there are fewer of them meaning fewer interfaces.

So, I’m wondering, what would be the advantage of one over the other (as your asking)? The only scenario I can come up with, is if there ever were a literal glue failure at the interface, the dovetail joint would have a mechanical advantage due to the opposing angles of the pins and tails by not easily slipping past each other. However, in my limited thinking, that seems to be a very unlikely event.

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im wondering what you using it for if its a small box then ya your right it does not matter if it going to hold up a heavy mass like the the shakespeare theater in london. that uses dove tails to keep the walls up as the building does not use nails. the dove tail is stronger because you cant pull it apart going in anyway but one. so you can pull on the joint and its stronger. but for the normal wear and tear of the household i use box joints unless i have a 3 year old then i poor it out with cement and still hope for the best.

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Matthias Wandel put this to the test and the finger joint won. In fairness to all the dovetailaholics out there, his test setup seems skewed in favor of the finger joints. He also admits that his finger joint has vastly more gluing surface and that the dovetails are half-blinds, not through.

box.jpg

But his conclusion is still valid: The strength of modern adhesives makes fancy joinery today less important than it was historically. You could certainly engineer a thorough, scientifically balanced test of dovetails versus fingers and you would probably end up with results such as the following:

  • A dovetailed drawer fails when driven over by a truck weighing 3200 lbs.
  • A finger-jointed drawer fails when driven over by a truck weighing 3275 lbs.

    ...and you'd be thrilled with yourself for having amassed such data. But then you'd have to admit that none of this matters because:

    • The wood itself had long-since been reduced to splinters before the 2500 lbs truck rolled over it and
    • I don't intend to drive over drawers with a truck.
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For general use I do not see any reason to discount either approach. Seems there is lots more glue surface on a finger joint and t he dovetails have the mechanical advantage (in one direction while being mechanically "held" by case sides in the other). No big deal. Both are legitimate.

Use whichever you prefer from design and construction point of view. It is nice if you get experience with each just to have richer background to assist those decisions. Of course I don't walk the talk as I've never made drawer with finger joints. But someday...

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Beechwood -

Either joint will work and will work well for a long time when executed correctly, so go with what is aesthetically pleasing, and what you are capable of making.

I agree with what Rob was alluding to. I think sometimes woodworkers have these types of discussions/arguments too much. Which one is stronger? Which one is flatter? Which one is faster? If they all work, then choose the one that works best for you. If joint A fails at 2000 lbs. or force, and joint B fails at 1800 lbs., well joint a is stronger, but if the joint only faces 500 lbs. then they will both work.

Of course this also sounds like a discussion that Chris Schwarz has with himself. I know it was in "The Anarchist's Toolchest", and I think he did a blog post about it, but his stance was that if you have to ask the question, you usually already know the answer. I'm guessing you already know the answer to the question you are asking, but you are looking for some validation to your own answer. Hopefully you found it here.

Jonathan

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if you have to ask the question, you usually already know the answer. I'm guessing you already know the answer to the question you are asking, but you are looking for some validation to your own answer. Hopefully you found it here.

Thanks all. I was pretty sure that finger joints with modern adhesives would be "good enough" for, say, a child's toy box that was expected to last indefinitely. But, I don't have lots of experience, and so I was wondering if maybe there was some issue I wasn't aware of.

One thing I've learned over the years is that I actually don't "know it all", and it never hurts to ask around.

Thanks again for all the responses,

--- Chip

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Thanks all. I was pretty sure that finger joints with modern adhesives would be "good enough" for, say, a child's toy box that was expected to last indefinitely. But, I don't have lots of experience, and so I was wondering if maybe there was some issue I wasn't aware of.

One thing I've learned over the years is that I actually don't "know it all", and it never hurts to ask around.

Thanks again for all the responses,

--- Chip

oh chip shure you know it all its just that what you know does not actuly have to be correct you just have to think its correct.

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That test is so far from a fair comparison I wouldn't have even bothered wasting time on it. Of course in that situation the box joint would be stronger, there are over twice as many fingers. Not only that, but the router cut joints tails aren't the full width of the board, as well as them being half blind. You can see where the dt joint failed, splitting the pin board, which wouldn't have happened had they been full through tails.

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