Table Saw Joinery: Tenons and Half Laps

One of the easiest ways to do tenons for a mortise and tenon joint and half lap joinery is to do that on a table saw equipped with a dado head. I'm gonna be doing that on this Laguna saw, one of the saws from their Fusion series, and take you through all the setup that we need to do in order to do those joints. Now, tenons, of course, are integral to a mortise and tenon joint, so that's where those parts are gonna come together. Half lap joints, what I really like about those is how incredibly strong they are. There's so much surface area there, that makes an amazingly strong frame.

So first step, dado head has to go on the table saw. And, of course, saw is unplugged for this. Get things up here where it's a little easier for me to my work. Let's do the tenons first and approach to this is always make the mortis, make the negative part of the joint, and then we're gonna make the positive, the tenon to fit it. So that's still unplugged, because what we need to be able to do is adjust the height of the blade.

We also need to be able to adjust the fence distance here. So here's the deal, I wanna produce a 1/4 inch tenon. This is 3/4 inch stock. So if I take 1/4 off the bottom and 1/4 off the bottom again I should have 1/4 left in the middle. I'm gonna use a piece of bar stock to set the height of my dado head.

And what I'd like to do at this point is have that dado head just a little bit too low. I can always take more material off. I haven't yet figured out how to put it back on. So I would rather have the tenon start a little too much big, and then we can reduce it if we need to. The other thing we'll do is we'll be using the miter gauge and feeding our material like this.

And it's the fence that's gonna control the length of the tenon. In this case, it's 1/2 inch long. One way we could do that would be put a sacrificial fence on here, bury part of that 3/4 inch dado head. The easiest way to get the dado head on there is to just build it up oversize, either bury part of it, or in the case of this saw what we can do is take advantage of this fence system. And by bringing the fence back here I can get this to where I'm only exposing the amount of dado head that I actually need for this particular cut, just like that.

Here we go. Like we thought, the tenon is too big. Now, keep in mind as you make these adjustments that the amount its oversized, we're gonna raise the dado head by half that, because we're taking a little bit off each face. So right there, I'm just over 1/16 strong. I'm just gonna keep going with this until I get it to scoot in there.

That looks good. Now here's what I'm looking for on the fit. I should be able to push that in by hand, like I just did it. Shouldn't have to drive it with a mallet. And when I lift, they stay stuck.

So there's enough friction there to keep them together. That's a great fit. Now, in cutting the complete tenon what'll happen is face, face, edge, edge, like this. That gives us the shoulders that we need on all four sides, so that we can put the joint together like that. One of things that's really, really important is that the piece you're doing your test cuts in has to be exactly the same thickness as your project material, because the resulting tenon, in the size of the tenon here is thickness specific.

So make sure you take care of that. Next thing, I'm gonna just change a couple of things around here and we'll have a look at half lap joints. Half lap joints are just what the name sounds like, which is we're gonna take half the thickness off of this piece, half the thickness off of this piece, put them together. And that's where that massive amount of glue surface comes from that makes it really, really, really strong. First step, set the height of the blade.

I've got, on this piece, the center of it is marked out. Just like on the tenon, what I wanna do, saw unplugged, is set this so it's a little bit below that point, same deal. We can do a test cut, I'll show you what I'm looking for. And then if that's, if we haven't taken enough off, raise the blade to take off a little bit more. All right, we're test cut ready there.

And here's the test. Put them together. If this is, if this face is higher than this face then the half lap isn't deep enough yet. Like the tenon, we take half this amount off. If that's 1/8, we raise the blade by 1/16.

There we go. Takes a few tests cuts, but once we get there, we're good to go. Next part of our setup, unplug your saw, and we need to locate the fence. To locate the fence I'm gonna use my project parts, bring the fence over. And I want a little bit of dado head sticking past the edge of this piece.

I'm using it as a gauge, the material. And the reason I'm doing that is when this joint is complete I want this end grain to project a little bit past the edge grain of the mating piece. Then, after the glue is dry, you can come back with a block plane or a sander and clean those up to make them flush. Now, before you cut project pieces, let's do one preemptive step. Lay out all your project parts and mark the side that will be up when you make the cuts.

The reason that we do this is when you really get going on a project if you make a mental error here and cut this end and then cut this end with a flip in between, that's going to be bad. We're not gonna be able to use that piece. So if I mark that, that's gonna keep in mind, that's gonna help me keep in mind. I should always be able to see that mark, cut an end, rotate, cut an end. Then we have two longs, two shorts, and that is how our frame is gonna come together.

And remember, I kept talking about the incredible amount of glue surface that we have between these parts. So when we glue this surface area if you wanna go one step further what's pretty cool is drill a couple of holes in here and you can drive dowels in there, dowels of a contrasting color. So maybe if you're working with maple, we use walnut dowels or vice versa. It's a really good joint. Laguna's Fusion series table saw provided a great way to make both our tenon and our half lap cuts.