Quite a few people emailed me about a viral video
showing a joint like this one, and the cool thing
about this joint is, it goes together straight
or at a right angle, like this
or at a right angle
like this.
The geometry of this joint is based on the
rotational symetry like this
so every time I rotate this cube by 120 degrees,
it's kind of in the same orientation it was before.
So, now if I slice this cube through
right along here, rotate that
by 120 degrees,
it's still a cube. So, imagine this split cube
being part of a larger piece of wood on
either side, and I've actually made another
piece of wood that has essentially this cube
here's one configuration, another,
and another. Now, this joint is
kinda boring because, well it doesn't interlock any
So, we want some kind of joint surface area
that can take orientations that are 120
degrees apart, and ideally for that would be
something like this, so I can put these pieces
together like so, or I can rotate one piece
120 degrees, and that's what I've done
with this one, we have
inside of here, the same geometry, which
goes together in three different ways.
Now, back to this cube, I'm gonna try
cut that joint on the bandsaw very crudely
and I'm gonna start by cutting a pyramid
off of either side and then the middle part
will form the joint.
So, now we have the middle layer
and I need to mark the geometry on here.
So, here's this, and if I take these away,
Then, that gives me that joint that's
just like this one in here.
And, because these ones have more area on the bottom,
I'll say those belong to the bottom,
and these three belong to the top.
It's a good thing I have the wood grain to guide me,
to know which way they're supposed to go on there.
So, I did this to both halfs, and now I can
put my cube back together, like this,
or rotate it and put it together,
or rotate it again.
So, let's go back to straight,
and let's attach a piece of wood to either end of this,
So, we'll make this
a big piece of wood.
And, on here,
Now, how do I get this cube apart again?
Thre we go. Oh woops.
I shouldn't have glued this part here.
OK, just scraped the glue off where it wasn't supposed to go,
and now I can assemble this straight,
or I can assemble it like this,
that's one right angle.
Or, like this.
Now, I'll try to recut this joint using some
nicer material, and the first thing I need to do
is to cut this corner off, and that'll form a
tiranglular face, if you imagine this
having not been cut, there would be a traingle right here.
I just marked on here, what parts need to be
carved away to make this
look like this one and I could try to
carve that away with a chisel, but
that would take forever, not my thing,
so, I'm gonna use the pantorouter.
To lay out the template for this joint, I made 6 triangles
with exactly 60 degree corners.
This was pretty tricky. The first two that I made
actually didn't quite work out.
But, on the third time I got it right
I'll use these to lay-out my template, like this.
OK, I got my work piece set-up on a V-block on the pantorouter
And this angle here is 35.26 degrees,
and I put a hole in the middle of my template,
so I could make sure that the bit ends up
in the middle, here. And, that's the only alignment
that I've got. And, in terms of depth of cut,
I have to make sure that the bit cuts as deep
as to this line, right here.
Both halves of the joint are identical
so making the other half is exactly the same procedure.
Well, I think I should have left a little bit of
tolerance in here. It does fit together
very nicely but I'm afraid if I push this all the way,
I may never get it apart again.
I added a bit of extra slack by carving it out a bit
with a chisel. And, now it goes together
fairly well. So, here's one right angle.
The other right angle,
and straight. So, how useful is this
kind of joint? Well,
not at all, as far as I'm concerned,
because it's way too difficult to get right.
You only want to make this type of joint if
you're looking for a challange or you have something to prove
and it's really not very strong because it just
doesn't respect the wood grain very much.
A much more practical joint that can go straight
and at a right angle would be a bridal joint.
Yeah, really not a very strong joint.
It just doesn't respect the wood grain.
This part just breaks off.