Large Compass – Trammel Circle Jig Tool

MembershipIf you’d like to sell prints of this model, you can do so by joining my Commercial License. It’s a simple way to support the project while getting permission to sell your prints

A simple way to draw large, accurate circles using materials you already have in your workshop.

This tool is designed for situations where a regular compass is too small – for example when marking tabletops, arches, or large cutouts.

Instead of relying on a fixed ruler system, it mounts directly onto a straight beam, giving you full flexibility depending on the material and length you choose.

🪵 Practical design

This is a fully 3D printed solution with no additional hardware required.

It is made to be easy to reproduce and use:

• No assembly
• No metal parts
• Uses standard workshop materials

📏 How it works in practice

Slide the two parts onto a straight beam, insert a pencil, and rotate around the center point.

The radius is defined entirely by your beam length, which makes it useful for both small and very large circles.

This makes it especially practical for woodworking tasks where dimensions vary from project to project.

🔄 Compatible materials

The design works with a wide range of common materials:

• Wooden battens
• Aluminum extrusions
• Pipes and tubes
• Straight scrap pieces

📦 Included sizes

Four versions are included to match different beam sizes:

• 21 mm – standard US lumber
• 40 mm – small profiles
• 55 mm – general use
• 75 mm – larger beams and pipes

🖨️ Print information

• PLA, PETG or ABS
• No supports required
• Designed for easy and reliable printing

🧰 Typical use cases

• Marking round tabletops
• Creating arches
• Large radius layout work
• General carpentry and DIY projects

💡 Tip

For better accuracy in hardwood, make a small pilot mark at the center point before rotating.

👉 Designed as a simple, flexible tool for real workshop use.