This project was built and designed by Billy from Newton Makes. It features a shop-made tenoning jig designed to simplify one of the most rewarding and precise joinery methods—the castle joint.
Rather than relying on complex setups or extensive measuring, this jig makes it easy to achieve clean, repeatable cuts. Billy’s design is approachable for all skill levels and offers an excellent way to level up your joinery game with just a few materials and basic tools.
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Why a Tenoning Jig Matters
Tenon joinery is a key element in strong woodworking builds, and a jig can make the process both faster and more accurate. Billy’s jig is designed to help woodworkers make repeatable cuts without the need for constant measuring or resetting.
The specific goal here is to produce castle joints, which are both visually appealing and structurally sound. With the help of this jig, you can easily cut the channels needed for the post and crossbeam pieces that form this unique joint.
Materials and Initial Setup
The jig starts with three pieces of MDF: a top, a bottom, and a vertical fence. MDF is chosen for its stability and resistance to warping, which helps the jig maintain accuracy over time.
An adjustable miter bar is installed underneath the jig to allow it to slide smoothly along the table saw’s miter slots. This feature not only makes the jig easy to use but also ensures future fine-tuning can be done without rebuilding it.
Routing for Smooth Operation
To begin, Billy uses a dado stack to cut a channel into the top piece of the jig. This channel allows the vertical fence to slide and adjust as needed during setup.
Once the initial groove is complete, additional channels are cut into both the top and bottom boards to install aluminum T-tracks. These tracks allow for the use of bolts and knobs that secure the jig parts in place while also allowing quick adjustments.
Strength Through Smart Assembly
Instead of glue, the components are fastened together using screws. This makes the jig modular and easy to disassemble for maintenance or recalibration.
A pair of 45-degree braces is added behind the vertical fence to give it added strength. This small but crucial detail ensures the jig remains rigid and stable under repeated use.
Sacrificial Reference Board
Billy attaches a replaceable reference board to the vertical fence. This sacrificial board provides a clean backing surface and protects the jig from wear during cuts.
Oversized holes are drilled into the reference board to make alignment easier. This also allows for quick replacement when it becomes too worn or damaged after repeated use.
Building the Castle Joint
With the jig complete, Billy demonstrates how it’s used to create a castle joint—a three-way connection involving two crossbeams and a vertical post.
Each piece is first milled to the same length to ensure symmetry and fit. Channels are cut into both crossbeams to receive the post, using the jig for guidance and consistency.
The center post then receives two intersecting slots to accept the crossbeams. Thanks to the jig, these slots are cut cleanly and with very little setup adjustment between passes.
Testing Fit and Making Adjustments
After each round of cuts, the pieces are test-fit together. If anything feels too tight, a quick adjustment to the jig or a second pass on the saw can refine the fit.
Billy emphasizes that it’s better to sneak up on the fit than cut too much at once. The castle joint relies on clean, snug connections for both strength and appearance, so precision matters.
Why This Jig Stands Out
One of the biggest benefits of Billy’s design is that it reduces the need for exact measurements. By referencing the position of one board against another, woodworkers can avoid common mistakes caused by measuring errors or tool drift.
The jig also supports repeatability. Once it’s set up correctly, multiple joints can be made without changing the settings—making it great for projects that require several identical parts.
A Joint Worth Mastering
The castle joint not only offers impressive strength, but it also brings visual interest to furniture and frames. When done well, it turns a simple table leg or cross support into a standout detail.
With this jig in the shop, creating these joints becomes far more accessible. It’s a great example of how a small tool can expand what’s possible in woodworking.
Please support Billy by visiting his website here: https://www.newtonmakes.com/shop.