Izzy Swan from izzy swan demonstrated the test featured in this video.
This video shows a homemade horizontal slot mortiser built from scrap plywood and an inexpensive trim router, designed to replicate and expand on the functionality of a Festool Domino at a fraction of the cost.
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Design and Purpose
The build is intended to perform horizontal slot mortising and additional joinery tasks without the high price tag of a dedicated machine.
Izzy focused on creating a versatile, low-cost platform that can make mortises, dowel holes, and elongated slots, while remaining easy to service and adapt over time.
Construction and Materials
The core structure uses plywood dovetail slides for linear motion rather than expensive metal rails, demonstrating a practical shop-made approach to motion control.
Components are largely shop scraps plus a trim router and hardware, keeping the total build cost well under what a commercial machine would cost.
Motion System: Plywood Dovetail Slides
Plywood dovetail slides proved surprisingly effective, providing smooth travel and simple maintenance if tightening or adjustment is needed later on.
Izzy notes that sawdust buildup was not a significant problem and that the slides can be re-tightened by shifting screw positions, which adds longevity to the design.
Router, Bits, and Cutting Strategy
The setup uses a trim router and affordable straight bits rather than large spiral cutters, prioritizing accessibility and replaceability of cutters.
Longer straight bits enable deeper mortises and step-through grooves, and although passes must be conservative, these bits are sharpenable and available in many sizes for varied joinery needs.
Alignment, Stops, and Accuracy
Alignment is achieved by locking start and stop positions on the carriage and lowering the router to engage the work, which produces repeatable mortises when matched tenons are prepared accordingly.
Izzy allowed a small amount of play in layout to ensure parts fit together cleanly, and the method delivered accurate joinery in testing.
Accessories and Additional Uses
Simple match-fit fixtures, toggle clamps, and a few shop-made accessories expand functionality for doweling, pass-through slots, and repeated layouts.
Shop-made dowels with relief grooves were used to ensure glue squeeze-out and improve glue surface, showing how small accessories can improve joint reliability.
Performance, Limitations, and Upgradability
The machine excels as a stationary shop tool that delivers professional-style results for a small fraction of the price of a dedicated commercial unit.
Limitations include a lack of dust collection and portability, but the design is intentionally open-ended so future upgrades (added dust control, refined slides, or alternate fixturing) are possible.
Cost and Practical Value
By using common materials and an economy router, the build demonstrates significant cost savings while retaining useful capabilities for joinery work.
For hobbyists or small shops, this approach offers a pragmatic trade-off: lower upfront cost and customizability in exchange for sacrificing portability and integrated dust management.
Overall Takeaways
This homemade slot mortiser illustrates how thoughtful design and basic shop skills can deliver a versatile tool that solves real workshop needs without expensive proprietary hardware.
Izzy’s approach is useful for woodworkers who want to experiment, tailor a tool to their workflow, and expand functionality beyond a single-purpose commercial device.
Conclusion
The project is a strong example of practical problem solving in the shop: it recreates core Domino functions, adds extra capability like doweling and elongated slots, and keeps the build accessible and serviceable.
Please support Izzy by visiting his website: https://www.izzyswan.com/.
Matt’s Take
These are my personal thoughts and tips based on my own experience in the shop. This section is not written, reviewed, or endorsed by the original creator of this project.
Izzy’s approach here really highlights one of my favorite aspects of woodworking — building the tools you need when commercial options are out of reach. The plywood dovetail slide system is particularly clever. I’ve seen plenty of shop-made jigs fail because makers overcomplicate the motion system, but this keeps things simple and serviceable. The fact that you can retighten by shifting screw positions means this jig could last for years with basic maintenance.
The router bit strategy is worth noting too. While spiral bits are ideal for mortising, they’re expensive and not always readily available in smaller diameters. Using affordable straight bits and taking lighter passes is a smart trade-off that keeps the project accessible. Just remember to go slow and clear chips frequently — straight bits can clog more easily than spirals, especially in deeper cuts.
From a safety standpoint, any shop-made router fixture like this needs solid work holding. Toggle clamps are your friend here, and it’s worth investing in quality ones. The forces involved in routing can surprise you, and having your workpiece shift mid-cut is both dangerous and frustrating. Also consider adding some form of emergency stop or easy router access — being able to quickly shut down or lift the router can prevent a small mistake from becoming a big problem.