Whether you are making a simple wooden box, a kitchen tray, cabinet drawers, or a chest, a box joint provides not only a firm and strong connection but also makes the joint stand out aesthetically.
A box joint, sometimes known as a finger joint, is one of the basic woodworking joints, which interlocks two pieces of wood together using pins.
There are a few ways how to build a standard box joint. You can lean towards the traditional way by using a hand saw and a chisel, or make a box joint on a table saw or a router table by using a table saw box joint jig or a router table box joint jig.
In this article, we will make a box joint jig for a benchtop router table I built some time ago.
One of the main advantages of a box joint jig is the simplicity and repeatability with which you will be able to create corner joints.
The box joint jig is an add-on to the benchtop router table I built some time ago. The jig slides around the table with the help of guide rails and uses stop blocks for precise cutting. This build does not use the embedded t-tracks on the router table however, it would be quite easy to build the jig in this way as well.
Read on to find out how to build a box joint jig for a router table, how to set it up, and how to cut box joint corners.
DIY Box Joint Jig for Router Table Video
If you want to see how it is done, watch the video below for a step-by-step guide on how to make a box joint jig.
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Table of Contents
- Box Joint Jig Video
- The Material you will need
- General Questions
- What is the difference between a box joint and a finger joint?
- What router bit for box joints?
- How to Make a Router Table Box Joint Jig
- Step 1: Build the Sliding Base
- Step 2: Make the Back Fence
- Step 3: Make the Front Fence
- Step 4: Test the Box Joint
- Step 5: Secure the Front Fence
- How to Use a Router Table Box Joint Jig
- Tips When Cutting Box Joints on a Router Table
*Safety is your responsibility. Make sure you know what you’re doing and take all necessary safety precautions while working with power tools. Safety comes first!
Always be cautious and careful when using any power tool.
Material needed to make a Box Joint Jig
Box Joint Jig
Plywood – 31cm x 10cm x 1,2mm
HDF – 48cm x 16cm x 0,5cm
HDF – 2x (30cm x 7cm x 0,8cm)
Spruce wood strips – 2x (28cm x 3cm x 1,8cm)
Wood Screws, washers
6mm straight router bit
Mini Table Saw
What is the difference between a box joint and a finger joint?
A box joint and a finger joint are very often incorrectly confused.
A box joint consists of multiple interlocking profiles along the entire length of the edge of both pieces of wood, which are then joined and glued. A box joint is typically used in making boxes and similar projects where a very strong bond is needed to support a lot of weight in a small space.
A finger joint consists of many small fingerlike pins that interlock together to join two pieces of wood. The pins are smaller and more delicate than in the case of a box joint. Finger joints are typically used when connecting long pieces of wood, in timber framing to create longer members than the original ones.
What router bit for box joints?
The best router bits for box joints are a double-flute straight router bit and a double-edge spiral up-cut bit. They both provide excellent results. The cuts are clean and precise and they leave a smooth finish.
To take it a bit further, the difference between a straight router bit and a spiral router bit is the quality of the resulting cut and the price. Although both provide great results a spiral bit leaves a smoother finish, reduces tear-out, and would be the better choice for making box joints. The increased price goes hand in hand with the quality provided.
Read the following article for more information regarding these router bits:
Let's start building!
The box joint jig (finger joint jig) consists of 2 main parts – the sliding base, and the back fence.
The sliding base is made of HDF and spruce wood strips, and the back fence is from Baltic birch plywood and HDF. The overall dimensions of the box joint jig are 48cm x 28cm x 13m.
NOTE: The box joint jig built in this article is designed for a clamp-on benchtop router table and uses 6mm router bits. Similarly, it can also be made for other types of router tables.
How to Make a Router Table Box Joint Jig
Step 1: Build the Sliding Base
First, measure the dimensions of your router table. Mine is 40x30cm.
Cut the HDF board slightly longer than the length of the router table leaving a four-centimeter overhang on each side (48cm x 16cm x 0,5cm). To make all the cuts I am using a mini table saw crosscut sled. It is easy to cut the board with and the cuts are clean and precise.
Cut two spruce wood strips to size and glue them to the HDF board. Make sure the strips fit snugly against the router table so the box joint jig can easily slide over it.
Turn the router table upside down, align the edges with the HDF board and clamp it to the workbench. Apply glue on the spruce strips and glue them to the HDF board.
Wait until the glue dries and secure the strips with screws.
NOTE: When you mount the box jig it should slide easily over the router table. If the grip is too tight, sand the spruce strips a bit. If the box jig wobbles add painter’s tape on the inside of the strips.
Step 2: Make the Back Fence
Glue 2 HDF boards on the box jig. One flat, the other perpendicular to the base making a back fence. When gluing the fence use a machinist square to make sure the fence is perpendicular to the base.
Mount the box jig on the router table and cut a kerf in the base until you reach the HDF back fence. Use the router bit you want to use for cutting the box joint (I am using a 6mm straight router bit).
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Step 3: Make the Front Fence
Temporarily attach the front fence to the back fence with clamps and cut a kerf in for the stop pin. The pin should be long enough to support wood pieces of different sizes (a protrusion of 2cm is sufficient).
Glue the pin in the cut slot and make sure it is flush with the bottom of the fence.
Step 4: Test the Box Joint
Make a few test cuts before fixing the front fence in position.
Mount the front fence on the box jig. Add a piece of wood (of the same size as the pin) between the stop pin and the router bit and fix the front fence with clamps.
Set the height of the router bit. The height of the bit should exceed the width of the cut wood piece by just a little bit. When you assemble the wood pieces the pins in the joints should protrude just a bit.
Make the first test cuts and see how the wood pieces fit together. Read below on how to use a router table box joint jig and refer to the video attached.
NOTE: If the fit is too tight, move a bit the front fence with the pin toward the router bit. If the fit is too loose, move the fence away from the bit. Test the box joint jig until you get a nice fit. You should be able to easily slip the joint together by hand and the joint should hold by itself.
Step 5: Secure the Front Fence
When you find the correct position of the front fence, attach it permanently to the back fence with screws.
TIP: Optionally, you can add stoppers on the router table. Working with them will be easier and will ensure that you do not cut more material than you would like.
Below is a picture of a finished router table box joint jig. A box joint is one of my favorite corner joints. It is strong, looks nice, and is easy to make.
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I hope the information shared in this blog post inspired you and now you are ready to make a few box joints. 😉
How to Use a Router Table Box Joint Jig
When joining narrow pieces of wood, make sure you have enough pins on both wood pieces. Ideally at least two pins on each of the wood pieces. Also, watch the video provided to better understand how to make box joints.
How to make box joints on a router table:
- Install the box joint jig on the router table.
- Set the height of the router bit. The height of the router bit should exceed the width of the cut wood piece by just a little bit. Protrusions will be flushed once the box is assembled.
- Place the first wood piece against the fence, the edge flush with the stop pin and secure the wood piece with clamps. Make the first cut.
- Move the wood piece onto the pin using the freshly cut slot. Make the second cut.
- Repeat the process until you reach the other edge of the board.
- Flip the board 180 degrees and mount the wood piece onto the pin using the slot closest to the router bit.
- Place the second wood piece against the fence, flush with the first wood piece and make the cut.
- Remove the first wood piece and continue cutting until you reach the end of the second board.
- Assemble the wood pieces
Use an orbital sander to sand the protruding pins flush with the wood pieces.
4 Tips When Cutting Box Joints on a Router Table
It is quite easy to cut a box joint. Once the box joint jig is set up, you can easily and repeatedly make all the cuts. Here are a few tips to help you create the perfect box joints.
- When assembling a box joint a little friction between the wood pieces is desirable. The joint should be neither too tight nor too loose. You should be able to slip the joint together by hand. A tight connection will not provide room for glue, a loose connection will not provide a sufficiently strong connection.
- Apply glue on both wood pieces. Make sure the glue gets on all the pins and cutouts. Excess glue will be removed later.
- Use a straight router bit or a spiral router bit when cutting box joints on a router table. Preferably a spiral router bit. The cuts are cleaner and reduce tear-out.
- Use painter’s tape to avoid tear-out and to provide a cleaner finish.