Low-Cost Router Trammel & Beam Compass
When I was building a round table, I needed an easy way to lay out and cut a large, accurate circle. Rather than buy a specialized jig, I came up with a simple solution using 1/2"-diameter electrical conduit and a few inexpensive hardware-store parts.
The result is an adjustable beam compass and router trammel that makes it easy to lay out circles and then cut them with a router.
Make an Adjustable Router Circle Cutting Jig
The conduit serves as the beam for both tools. For the beam compass, I attached a pencil using a plastic cable clamp.
To turn it into a router trammel, I made a custom router baseplate that fastens to a conduit coupling.
A second coupling holds the centerpoint. I made this from a longer screw by cutting off the head and grinding the end to a point.
The screws that fit the coupling threads are available at most hardware stores.
Modify the Couplings for Easy Adjustment
There's one small modification you'll need to make before assembling the jig.
Standard conduit couplings have an internal ridge that prevents them from sliding completely over the conduit. I used a file to remove this ridge.
Once the ridge is removed, the couplings can slide along the conduit. Simply position the centerpoint at the desired radius and tighten the screw to lock it in place.
With this simple setup, you can lay out a circle with the pencil attachment, then switch to the router to cut the same shape.
For routing, secure the workpiece, keep the pivot firmly anchored, and make the cut in multiple shallow passes.
It's an inexpensive, adjustable jig that's especially handy for round tabletops and other curved woodworking projects.
More Woodworking Tips & Techniques
Building an inexpensive router trammel is just one way to make your time in the shop easier and more productive. Sometimes, the simplest tricks can make the biggest difference.
Explore our Tips & Techniques collection for practical, shop-tested ideas from Woodsmith readers. From clever jigs and joinery solutions to sharpening, sanding, and finishing techniques, you'll find plenty of useful tips to put to work on your next project.
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