Hi everyone, and welcome to Bob's Wood Stuff.
Today we're gonna do the first week of my new series, which is called Joinery Class.
This week we're making a 3-way lap joint.
These joints are really good for trivets to put hot foods on,
or for the tops of coat racks.
I've also used one for the top of my May pole.
If there's another joint that you'd like to see, let me know in the comments.
This works similarly to a half lap joint
but because there's three that need to overlap,
each piece only has one third of the material present,
and two thirds is removed.
The first thing I need to do is make this lap joint.
And then once I have this X,
I can remove that middle section for the third piece.
I'll take these two pieces and find the center lengthwise.
Now what I need to do is overlap them at a 120 degree angle
like these ones.
So now I'll set my protractor to 120 degrees,
and I'll mark a line at that angle.
This gives me one edge for my piece
and I can place it right against that.
So what I'll do is hold this piece down,
and I'll scribe a line on both sides of it using the marking knife.
I'm having a problem with this shifting a lot,
so I'm gonna clamp it down to my bench.
Now that I've marked the 120 degree diagonals,
I need to mark two thirds of this using my marking gauge.
My piece is three quarters of an inch thick,
so I'm gonna set my marking gauge at one quarter of an inch.
I'll do that by just placing a notch
and then putting the blade of my marking gauge inside that notch
while it's loose,
and butting the fence up against the workpiece.
I need to remove two thirds of the actual piece,
so from the bottom I will make my mark.
And then from the bottom from the other side I will also make a mark.
Now that I made those two marks, I'll use a square to connect those lines to the top.
Now I need to saw on those lines and remove this middle chunk of the piece of wood.
Before sawing anything, I need to create a knife wall on these shoulders here,
and I'll do that with my chisel.
With the flat side of the chisel against my mark
so that the bevel is going into my waste side,
I'll use the chisel to mark a straight ap-and-down line,
and then remove a small chunk by pushing into it.
This is called a knife wall, and that ensures that my shoulder is exactly where I marked
it,
and it doesn't get messed up while I'm sawing.
Creating this knife wall also cuts the fibers, so that when you're sawing it,
they don't tear out where you dont want them to.
I'll also create a knife wall on the other two sides that I need to cut.
Now I need to saw this using my Japanese saw.
I'll just place the saw blade directly into that knife wall that I made,
being careful to maintain that shoulder.
Even though these saws cut on the pull stroke,
I like to push it forward first to create a really shallow kerf
before getting that resistance from the teeth.
I'm only sawing on the two sides I can see,
which are the top and the side closest to me.
And then I'll flip it over and saw from the other two sides.
And then the same thing on this one,
I'll saw the top and the side closest to me.
Now flip it around and do the same cut from the other side.
If I've done this correctly, there should be a peak in the middle,
because I've gone in diagonally from each side.
So now I'll do a straight cut to get down to my line.
Make sure to look from the other side, so you're not going too low.
Now that I've cut these kerfs, I can chisel out most of the material,
while not going all the way to my line, because I'll use a different tool for that.
I'll chisel out this waste,
taking off about one eighth of an inch at a time.
Notice that I'm not chiseling all the way through.
I'll come in from the other side to remove it,
because I don't want the grain blowing out.
Now I'll flip it around and come in from the other side.
Now that it's really close to the final measurement,
I'm gonna use this router plane to get a smooth, level surface.
Now that this one is cut exactly how I need it,
I'll just place it on top of the other piece.
So this fits really well; it's very snug.
Ideally, it's gonna be really snug, or even a little bit too tight.
If it's too tight, you can do a couple passed on the hand plane
on the sides of this until it fits really snug.
If it's too loose, you might wanna re-cut it, because you really don't want it loose.
I'll place it right here, and then I'll use my marking knife to trace the intersection.
So now I need to remove this part, going down by one third,
because this one will be this piece, where the middle third is still present.
So I'll use my marking gauge and measure down one third
on both sides.
Then I'll take my square, wrap those lines down.
Take your time on this part, because if your markings are not accurate,
your joint won't fit well.
Okay.
Now I'll cut it down the same way as the previous one,
but I'll only go one third instead of two thirds down.
And I'll chisel out some of the waste.
Now I can use the router plane again, and I'll have to reset it to this depth.
Now I'll test the fit of it to see if I need to adjust anything.
That's pretty much a perfect fit, so I think I can move on to the next step
which is routing out an area for this third one to go.
I'll start by marking the middle of this piece, which will help me align it.
I'll use my centering jig to mark a line down the center of this last piece.
Now I'll place the X top-side-down on this third piece,
lining up the middle of the X with the center line.
Now that I've marked these lines I know that I need to remove a third of this out of both
pieces.
So I'll mark that using my marking gauge.
And I'll wrap these lines around using the square.
Now that the lines are drawn, I'll make a knife wall with my chisel.
After using the router plane, this third piece should rest into the groove.
I'm gonna make four cuts on this,
because I need to come in from both sides and four different angles.
Sometimes the fibers get stuck, and I'll need to do a little bit of cleanup with a chisel.
Now that that last piece is cut,
I'll see if it fits into the other two pieces.
It's not quite there yet.
I'm gonna clean it up a little bit with a chisel to try to get that fit.
Alright, I'll try to fit it again.
Cool!
So that is the three-way lap joint.
It's a pretty cool joint, it's mostly decorative,
but if you need this shape, it's really the way to go.
And just by doing it you'll get a lot better at joinery, because of the practice.
If there's a joint you'd like to see, please write it in the comments.
And make sure to like and subscribe.
Thank you so much for watching. Bye.