Mastering the Art of Cutting Tenons with a Router Table

One of the easiest ways that you can cut tenons on the end of rails is right here on the router table and I'll walk through that. First let's talk about the geometry of the joint. So you understand the dimensioning of it, as a general rule of thumb, what you wanna do is make the 10 and one-third the thickness of the overall thickness of the rail. So on a piece of three-quarter inch stock, like I have here, we'd have a one quarter inch thick tenon, then to get this dimension, the length of the tenon we're gonna take that one quarter, multiply it times two that gives us this dimension. So a quarter inch, 10 inch, shouldn't be about a half inch long, here at the router table, I've put in a three-quarter inch straight bit. We'd like the diameter of the cutter to be slightly greater than the length of the tenon that you wanna make. That's the easiest way to do the setup. Now think about what needs to happen here. We're gonna take away a quarter and a quarter and leave a quarter here in the middle. So what I'm gonna do for my setup with the router unplugged, is I'm gonna set the height of the bit. So it's just below this quarter inch bar stock. The bar stock is really a wonderful way to do setups, much easier than measuring. So right there, I'm just a smidge below. Now, the next thing we need is where does the fence go, in order to get our 10 in length. I've got another piece of bar stock for that. This is half inch. So I'm gonna use that with the bar stock against the face of the fence. I'm feeling the cutter out here where it projects just slightly past it tapping the fence I'm bringing it out to where they're even I'm gonna lock this end and do one more small adjustment by pivoting, right to there. When we feed the material, you need to have a backup board and that's gonna do a couple things. It's gonna prevent this from chipping on the exit side. It also acts like a big miter gauge to just helps square everything up makes us a whole lot safer. So we'll do a test cut here compare it to our mortise and see what we've got. Here are the mortises for my project cut with a quarter inch router bit. And when I lay my tenon on here I can see that my tenon is still too big. That's good. It's easier to make the tenon smaller than it is to put material back on. So that's why I'm starting with a bit too low in the table. That way it can kind of sneak up on my setting. That's one check I wanna make the other check is the length of the tenon. The easiest way to do that is come back to my bar stock put that up against the shoulder, on the tenon and then feel it out here to make sure they're flush. If they are your tenon length is good. Now, as I look at this, I'm gonna say I am a little over a 16th, too thick. So this is where having a router lift in your table is really a nice thing. A full revolution of this, is a 16th of an inch. So I'm gonna go a 32nd plus just a little bit. That's raising the cutter, do another test, cut, check the fit again till we have that dialed in just right. Once the fit is good, and what I'm looking for is the ability to just push that in by hand. Like I did, shouldn't have to drive on this with a male in order to get that to go in. Now he can completely cut the tenons and most cases your mortises are gonna look like this. And what that means is we're gonna cut three sides on this piece in order for this rail to fit into that mortise. So that looks good. Need just a little bit more work in order to round that tenon. So it sockets perfectly into the mortise, when I'm making the tenon, that will go into this mortise. It's gonna take one more cut. I'd create a shoulder on the bottom and on the top so that we can go into that mortise there where the mortise is blind. So router table is a great way to do it. Don't sweat it. If you don't have a router lift you can still do the same setup by adjusting the height of your router until the fit is perfect. So you have great mortise and tenon joinery for your project.