A Simplified Router Fence Setup

I want to help you out with the layout on a couple of joints that I have watch people struggle with in their wood working shops, one is a lock miter, the other is a mortise. The lock miter is a great joint once you master it. Have a look at one here. What we get is a great look on the outside because the parts are mitered so we have no end grain showing on the outside of the joint. On the inside we have a great mechanical grub, thanks to the way that this thing actually kind of tongue and grooves together. There’s a lot of automatic mechanical structure to this plus significant amount of glue surface. So once this is glued together, it’s really strong.

That’s the good news. The bad news is a lot of people struggle, making a lock miter because both the height and a bit and the fence location have to be just perfect. So here's the way I’m going to make this happen. Using this tool which has a ½ inch diameter pin in this end, I’m going to put that half inch pin the in the corner of my routers. Once the routers are on the table, I can open the vise on this and notice it has the vise slides. This nose out here is sliding as well.

So then I can take the material from my project, squeeze it in here and automatically get the fence location. That’s going to come off of this small pin up here. So thanks to the mechanics of the way that this device has been figured out, I can automatically get my fence in exactly the right spot for the particular lock miter bit. So let me show you now that you’ve seen the overall here, how this actually works in the router table.

First step, get the router in. Drop the large pin into the lid. Bring the fence forward and put my project material in the vise. Now the fence can just kiss that small pin right there, lock that fence some place. So now at this point, we’re not going to want to mess with that fence anymore. Thanks to this device it’s perfectly face. It’s perfectly aligned for this cutter so we can pop this out and put the lock miter in.

Now remember I said that where people struggle with the lock miter is the fact that you got to work and think in two dimensions. We have to get the ladder of dimension right, that’s the fence location. At the same time, in order for a lock miter to cut perfectly, we have to get the vertical dimension right, that’s the height of the bit. Well thanks to the way we’ve set this up and with the addition of another tool here, I can make this happen pretty easily.

What I’m going to do now is take this measuring tool. It has a pin on it that’s thin enough on the end to go into the slot on the lock miter bit. So what I’ll do is I’ll bridge the fence, allow that pin to sit into the slot in the lock miter. Now, I’ve got the offset that I created in the fence, lock into this tool, now I can use it this way and dial in the height of my cutter. Lock the height. With that, we’re set to make a lock miter in our material. Now remember when you do a lock miter, one face will feed down on the table with end grain against the fence like this. The mating piece is going to feed end grain down on the table face against the fence.

So in this case, we can’t have the guard on here because we have to be able to past over the cutter. Let’s do a cut and see what we have.

[Demonstration]

Now, let’s see our joint here. That piece that way, this piece this way, closing a very, very nice lock miter. Great fit between those two parts. You know a lot of times it takes me a number of test cuts to get to the point where I’ve got everything work and just right like it is on this one here. Part of the beauty of the system is when I put this in a close position, and off set number here that’s provided by the manufacturer lock miter bit by lock miter bit slightly different number for each bit that gets this part of the jig, correctly positioned, it makes it very, very easy to set up these lock miters.

Now, let me show you a little bit about mortises. For mortise layout I’ve got a couple of legs here I need to cut mortises into and in this case, what I want to do is I end up with a mortise that’s centered on the leg. Now if the leg is a perfect inch and a half, it’s a perfect 2 inches, mathematically finding the center isn’t the big deal. Sometimes by the time these parts are machined, there are a little bit of a funky size. Let’s say it’s an 1.716” instead of 1.5” finding the center by math can be a little bit tough. So let me show you how I’m going to do it.

Back to my jig, I’m going to take this lock miter offset off the jig and close this, lock that pin back in place. So basically what happens here is that as I move the vise, I’m on a 2:1 ratio with the movement of the arm on this end. That’s how I find the center stuff so easily. So now on my plunge router which I’ll use for cutting the mortises, I’ve got it equipped with the fence, the half inch pin goes into my router caulk lip just like I did on the router table. My leg goes into the vise, lock that in place. Now regardless of that leg size, when I slide my fence over like that and lock it in place I’m perfectly located here so that the distance from here to the center of the caulk lip is exactly to the center of the leg.

Now if you think about it a little bit, doing a mortise like this let’s say I don’t want the mortise in the center, let’s say I want it offset toward the outside, I can figure that out if I had a three quarter inch piece of material and I want it an 8-inch reveal on it that would make it a half inch to the center of the mortise. So instead of actually using my leg, I can put a 1-inch piece in here, close the vise and that 1-inch piece and that would give me a perfect half inch to the center of my mortise, so very, very easy way to find center on mortises.