Very thin utility knife, 6mm thick (1/4 inch) for standard utility blades. Glue the two housing halves together, the parts have pins and holes for easy positioning. The wheel might not immediately move smoothly, just work it a little bit and it will be fine.
blade_holder.stl | 16.3KB | |
blade_holder_bolt.stl | 80.7KB | |
left_housing.stl | 60.5KB | |
right_housing.stl | 58.3KB | |
wheel.stl | 215.0KB |