Box Joint Jig Video: How to Make a Box Joint Jig/Finger Joint Jig for a Tablesaw
David RadtkeBox joints, also called finger joints, are a great way to join corners on a box. Not only do they add a significant amount of strength, they also look great. Especially when the box joint is made from contrasting materials. The table saw, equipped with a dado head, provides a great way to make box joints, provided you have a jig. WWGOA’s box joint jig video shows a simple shop-made box joint jig is the perfect solution to your box joint needs.
The plans for this jig can be found here.
Here's the box joint jig. As you can see, it cuts nice, evenly-spaced fingers for the box joint, so that we can get a nice fit. Now, I'll review some of the parts of the box joint. We'll come in a little bit closer, but keep in mind you can make this from any scraps that you have in your shop. You just need 1/2 inch and 3/4 inch plywood, a piece of two-by-four, and some hardwood for a runner.
The runners fit into the Mitre slots. It should fit tightly. You don't want any play. And this fence is adjustable, so that we can adjust the fingers. You'll notice that this one is a tad bit loose.
I'll show you how to make the fingers a little bit fatter so they fit tighter. So, let's come in a little bit closer and take a look on how it's made. Okay, let's take a little bit closer look at this jig. Now, I said we had to make our finger joints, these are the ones that we just cut and they're a little bit loose. We want to tighten up the joint.
So, I'm gonna move this fence in this direction. Now, if we turn this jig around, you can see that there's some screws here. Now, these screws are into elongated holes in this sub fence. That means that if I loosen this, I can move this adjustable fence left and right just an 1/8 inch one way and an 1/8 inch the other way, which is more than enough. Remember, that when we set up this space between the pin and the slot, it's exactly the same as the width of the Dado blade.
So, that's our reference point to start with. Now, I've put this tab, this hardwood tab on here. And I had cut these two surfaces flushed, but I put a washer behind this tab. Now, what that washer does is it gives me a distance and that's a fixed distance to start with. And if I put my feeler gauge in there, I've got about 40/1000 on an inch.
Now, what I would like to do is move this, this way to kind of fatten up the fingers and get a tighter fit. So, I reduced this about 3/1000 of an inch. So, what I do, loosen the screws and then I select a blade configuration that gave me 37/1000, I had 40, and I tap this until that was tight. And when that was tight then, so I can just tap this lightly, this fence. Then, go ahead and tighten in down.
And then I try another test fit. From experience, I know that that would tighten that up just enough. So, then you'd go ahead, start a new blank, make some new test cuts. And I've already done that with this one. And you'll notice that the joint holds together nicely.
It doesn't fall out due to its own weight. And you can see that the joint has protruding fingers, so they stick out past the surface, which is exactly what I want. If the fingers were not protruding out and if they were actually below the surface, then your blade would be too low. And if they're up too high, this is less than a 1/16, which is ideal. Then, my blade is just right with this, but if they were like an 1/8 inch out, then I would have to lower my blade.
Now, keep in mind that if you raise the blade too much on this jig, you'll tend to get some tear-out because this now is set for this height. And if I were to cut some thicker material like 3/4 of an inch and then go back to cut 1/2 inch material like we've just cut, then I can get some tear-out in the back. Then I'd have to make a new fence here, a new adjustable fence, and then start over again. But, pretty easy. These are just plywood scraps, you probably have plenty of these lying around the shop.
So, that is the basics of this jig. It's a great little jig. It will last for many many cuts. Remember, that you want it to fit nice and tightly, but slide freely. If there's play left and right like this, you're gonna get sloppy joints and no amount of adjusting will make it right, so...
That's it. Make yours and enjoy the world of box joint.
Great to know how to adjust the jig but how did you make it from scratch? Mostly curious about the pin and space between pin and blade.
Some years ago, I made an elaborate—many might say ridiculously so—jig which is somewhat similar to Matthias Wandel's screw advance box-joint jig, but varies in many ways. It does however have a gearbox facilitating a moveable carriage. I had never been able previously to escape the problem of compounding whatever original error might exist in the first cut, e.g. being a thou off in the first cut will create an error of two-hundredths in the twentieth. I just don't know how to avoid the problem this way.
It didnt say how to make the jig
This tells how to adjust the jig but nothing about how to use it. I need to know how it's used starting with the blanks.
Where can I get the plans for this box joint jig? The link does not show up on my iPhone.
Just a suggestion, how about making the links in the articles a little more obvious. I'm color blind and had to mouse over the article looking for my pointer to change. Color seems like an obvious indicator but not for everyone.
HE explained how to use it, but not how it was constructed. It look simple.
Understand the making of box joint jig but no mention of the making of the pin?