Malcolm Schweizer
12-29-2013, 2:57 AM
Good day all,
I woke up tonight thinking about the "Impossible Dovetail" joint where the joint appears to be dovetailed from the front and top, so how could it possibly have gotten in there? Of course the answer is that it is a hidden sliding joint that angles in to fit (short version of the story).
Well, at 2:30 AM I got out the iPad and a broken stylus (so I am sorry for the sloppy drawing) and sketched an idea that came to me for what I am calling the "Implausible Dovetail," i.e. It's not quite impossible but still hard for someone to figure how you did it! Also this may just be more stable in the end than the impossible one.
Basically you are going to glue up two boards, but insert them separately to make the joint. They will slide in individually, pre-glued, and be clamped up after being inserted. For the sake of explanation, let's use an example of building a Ruobo bench with a dovetailed leg:
You would start by sawing the dovetailed recess into the top for board 1, sawing all the way to the end of the recess for board 2.
Chop out the waste.
Next, where board 2 meets board 1, from the top of the bench you will chop the joint straight down so that the mortice for board 2 is now a simple dovetailed mortice. Board 1 remains a complex dovetailed joint. Again, the joint started out as a dovetail, but hidden behind the line where board 1 joins board 2, you are chopping it straight down. The top will still appear to be double dovetailed.
Now there will be room to slide board 1 up into the recess for board 2, and then slide it forward into its place.
Next, glue up the face of board 2 and drive it into place. Since it is only dovetailed one way, it will slide in behind board 1, locking the joint.
The two boards are clamped while they cure, ultimately becoming one glued-up board. The appearance from the front will be a dovetail, and also from the top it will appear as a dovetail. With good grain selection and orientation the glue line wouldn't be too noticeable at the top of the joint, and even if so it still would be hard to figure out how you made the joint work.
So to recap, basically you are doing the joint in two halves and gluing up the two-piece leg while it is in the joint. The smaller dovetail of board 1 fits into the hole for board 2 and then slides forward to lock into the joint. Board 2 is driven in behind it, and the legs are clamped up. Once the glue dries you have a solid interlocking joint that will not move in any direction. Even if the glue fails, you still have a strong joint because board 2 is holding board 1 in place.
Has this already been done before? Did I overlook anything here that would prevent this from working? I see one flaw: If you ever plane the top, the secret would be revealed, as board 2 widens as you go deeper into the top compared to board 1. For that reason, perhaps this is not a solution for a Ruobo bench but rather for a table where it is not likely that you will be redimensioning the top down the road. So perhaps not the greatest solution, but something easier to make than the more complicated "Impossible Dovetail." That's why it's only the "Implausible Dovetail"!!!
I woke up tonight thinking about the "Impossible Dovetail" joint where the joint appears to be dovetailed from the front and top, so how could it possibly have gotten in there? Of course the answer is that it is a hidden sliding joint that angles in to fit (short version of the story).
Well, at 2:30 AM I got out the iPad and a broken stylus (so I am sorry for the sloppy drawing) and sketched an idea that came to me for what I am calling the "Implausible Dovetail," i.e. It's not quite impossible but still hard for someone to figure how you did it! Also this may just be more stable in the end than the impossible one.
Basically you are going to glue up two boards, but insert them separately to make the joint. They will slide in individually, pre-glued, and be clamped up after being inserted. For the sake of explanation, let's use an example of building a Ruobo bench with a dovetailed leg:
You would start by sawing the dovetailed recess into the top for board 1, sawing all the way to the end of the recess for board 2.
Chop out the waste.
Next, where board 2 meets board 1, from the top of the bench you will chop the joint straight down so that the mortice for board 2 is now a simple dovetailed mortice. Board 1 remains a complex dovetailed joint. Again, the joint started out as a dovetail, but hidden behind the line where board 1 joins board 2, you are chopping it straight down. The top will still appear to be double dovetailed.
Now there will be room to slide board 1 up into the recess for board 2, and then slide it forward into its place.
Next, glue up the face of board 2 and drive it into place. Since it is only dovetailed one way, it will slide in behind board 1, locking the joint.
The two boards are clamped while they cure, ultimately becoming one glued-up board. The appearance from the front will be a dovetail, and also from the top it will appear as a dovetail. With good grain selection and orientation the glue line wouldn't be too noticeable at the top of the joint, and even if so it still would be hard to figure out how you made the joint work.
So to recap, basically you are doing the joint in two halves and gluing up the two-piece leg while it is in the joint. The smaller dovetail of board 1 fits into the hole for board 2 and then slides forward to lock into the joint. Board 2 is driven in behind it, and the legs are clamped up. Once the glue dries you have a solid interlocking joint that will not move in any direction. Even if the glue fails, you still have a strong joint because board 2 is holding board 1 in place.
Has this already been done before? Did I overlook anything here that would prevent this from working? I see one flaw: If you ever plane the top, the secret would be revealed, as board 2 widens as you go deeper into the top compared to board 1. For that reason, perhaps this is not a solution for a Ruobo bench but rather for a table where it is not likely that you will be redimensioning the top down the road. So perhaps not the greatest solution, but something easier to make than the more complicated "Impossible Dovetail." That's why it's only the "Implausible Dovetail"!!!