If you’re reading this post, you’re probably trying to create finger joints (AKA box joints) for your woodworking project. Which means that you probably already know what they are.
But in case you aren’t sure, below is a rough diagram of the concept.
Finger joints are basically a more simplified version of dove-tail joints, which are the gold standard for woodworking.
But dovetail joints (above) are super tough to do because of the intricate angles of the cut, and if you’re just starting out or you don’t require the added strength of a dovetail, finger joints are an attractive alternative.
So this is how to make basic finger joints effectively using a routing table.
What You’ll Need
- Router/Routing Table
- Straight Routing Bit (the bit size should be the size you want the teeth in the joint to be; in this example I made 1/2″ cuts)
- Wood Glue
- Rubber/Wooden Mallet
- Flat File
- Clamps (corner clamps if you have them, but any will be helpful)
- Wood, obviously (I was using 1×4 pieces)
- Scrap Wood (this is useful for pushing your pieces through the table if you don’t have a table with a built in mechanism)
- Eye and Ear Protection (I’m not a stickler for woodshop safety, because that would be hypocritical, but seriously…you’ll want both when working with a router)
Step #1: Plan Your Cuts
Full disclosure: I’m not known for “planning” out my projects. Sometimes I draw drafts, but I rarely stick to them. More commonly, I decide what I want to do and just wing it.
But when it comes to making finger joints, I’ve learned the value of planning the hard way. The first time I ever attempted this, I literally went through four 8-foot boards just trying to make a small 12×12 box.
So the first step is figure out where you’re cutting.
Again, I was using a 1/2″ bit, so if you’re using a different size you’ll need to recalculate and do your own plan.
I used 1×4 pieces for this box.
- This means that the actual width of the surface I’m working with is 3.5″
- That equates to 7 sections that are 1/2″
- So for the first board, where the teeth are on the top and bottom, there will be 4 teeth and 3 grooves
- The second board will be the opposite (3 teeth and 4 grooves)
The next step is to figure out how to create the grooves (AKA, where the router should be set to make the cut in the right place)
- Using a half inch bit means that the range of the cut will be 0.25″ to the right of the setting and 0.25″ to the left of the setting
- See below for the examples of this
I can’t emphasize this enough: WRITE IT DOWN!
Write down where you should be cutting on both boards.
Actually, I color on the board with my pencil so that I can see where the grooves are supposed to be.
Seriously, take the time to be meticulous about the measurements before you start cutting, because if you mess it up you’re starting all over again.
Step #2: Set your router
- Set your router for depth
- Your grooves should be as deep as your boards are wide
- In this case, the actual width of the 1×4 is 0.75″
- So your router bit should be set to a depth of 0.75″
- Set your router for your first groove
- For the first groove on board #1, you need a groove from 0.5″ to 1″
- So (see above) you should be setting to cut at 0.75″
<–This picture shows something that most standard routing tables (of the modern era) feature: measurements.
You can use these to get a rough idea, but I strongly advise that you do not trust them.
For example, the measurements on
my routing table are about 1/8″ off. This may seem really arbitrary, but in the case of making finger joints, that small error can really screw you up.
So be sure to check your measurements the “good old fashioned way” and get your tape measure out –>
Measure from the fence to the center of you the bit.
Step #3: Do it to it
This part is easy.
This part is also dangerous.
Please be careful.
Hints and Tips: I make two passes for each groove. It makes the next step easier.
Also, do not rush the piece through the router. This leads to splintering, and that’s something that sanding just doesn’t fix. Patience is key.
Step #4: Putting it together
Assuming you’ve cut all the pieces correctly, you should not be ready to assemble them.
First, you want to file down the imperfections in the grooves.
Again, if you’ve been precise about your cuts, these are incredibly tight-fighting joints. Even the smallest piece of sawdust or a splinter can make it impossible to fit the teeth in the grooves or, worse, it will cause you to split the wood or break off teeth as you put them together.
So, much like sanding in general, this isn’t the most fun part of the project, but filing is a very important part if you want a nicely finished product.
Using a flat file, gently file down all edges inside the grooves. Pay special attention to getting the reside out of the corners.
Now you’re ready to start putting it together.
A lot of carpenters recommend that you dry-fit your joints to make sure they’re perfect before adding glue. On one hand, this is a good idea. But on another hand, if you’ve made really tight fighting joints, it’s not always a great idea: repeatedly putting them together and taking them apart increases the likelihood that you’ll cause damage, split wood, or break off teeth. So that’s your call. But I don’t dry fit.
<–Put a little bit of wood glue in the joints. To be honest, the amount of glue I used in this picture is probably excessive. It doesn’t take a lot.
Now you very slowly start to slide the pieces together. This is slow and tedious, and you have to be careful. It takes a lot of wiggling and a lot of patience.
Once you have the joint started, use a rubber or wooden mallet (NEVER a hammer) to slowly tap the pieces into place. I suggest alternating the direction you fit from (i.e., hammer on one side a few times, then hammer on the other).
TIP: It can be tempting to just hammer the shit out of the thing to get it together…but resist the urge. Slow and steady prevents splintering or chipping the teeth . And you don’t want this to happen to your joints…look how crappy that looks. You can’t sand that away ———>
And voila. You’ve created finger joints.
Teaser: Below is a picture of what I was making from this box. Look for an upcoming post to see the custom chisel box I made as a Christmas gift.