Circle Cutting Baseplate/Jig for Bosch Colt 1HP Palm Router PR20EVS

Bosch Palm Router Circle Cutting Jig (Small Radius Capable)

This is a custom circle-cutting jig designed for a Bosch palm router, with a key improvement over most existing designs: it allows the pivot point to sit directly underneath the router base. This enables cutting significantly smaller circles than traditional jigs, which are typically limited by the pivot being offset from the router body.

The jig replaces the stock baseplate and features an adjustable slot that holds an M4 bolt and nut, which act as the circle’s center pivot. The slot includes recessed regions on both sides, allowing the pivot point to slide beneath the router footprint—making small-radius cuts possible.

How to Use

1. Drill a 4 mm (or 5/32") hole at the desired center of your circle.

2. Adjust the jig to set your desired radius using the M4 bolt.

3. Insert the bolt into the center hole.

4. Power on the router and cut your circle.

Design Notes

• The ability to position the pivot under the router is what enables very small circles.

• The recessed slot geometry allows full adjustability across a wide range of radii.

Important Tip (Small Radius Use)

If you plan to cut small circles (where the pivot sits under the router), consider modifying the M4 screw for easier adjustment:

• Cut a slot or drive feature into the tip of the screw (e.g., with a Dremel).

• This allows adjustment from the underside of the jig.

Without this modification, you’ll need to remove the baseplate from the router to adjust the pivot position when it’s under the tool.

Print Settings & Material Recommendations

• Material: PLA works well and is what this model was tested with. Most rigid materials (PLA, PETG, ABS, etc.) should perform well.

• Walls/Perimeters: 5 walls recommended for stiffness

• Supports: Required — the recessed slot on both sides creates overhangs in any orientation

• Infill: ~15% (not critical—use your typical default)

• Layer Height: Standard (0.2 mm recommended)

• Orientation: Print flat on the build plate

• This part benefits more from wall thickness than high infill—prioritize perimeters for rigidity.

Required Hardware

• 1× Bosch PR20EVS palm router (or compatible baseplate pattern)

• 1× Printed circle cutting baseplate

• 1× M4 nut

  • ~6.9 mm across flats (< 7 mm) this is important for easy adjustment

  • Thickness < 3 mm

• 1× M4 × 12 mm machine screw

  • Head diameter < 8 mm

  • Head height < 2.5 mm (button head recommended)

Optional

• Dremel or similar tool (for adding a screwdriver slot to the screw)

License & Attribution

This design builds on the Bosch Colt palm router baseplate by Morfesto on Printables:
https://www.printables.com/model/883735-bosch-colt-palm-router-base-plate-pr20evs/files

That model is licensed under GPL v3.0, so this one is too.

Feel free to use, modify, and share this design however you’d like (including commercially), just make sure to give credit and keep any derivatives under the same GPL v3.0 license.

Description was written with the assistance of AI