Building the router copier
Router mount and carriageThe router mount and carriage provides three degrees of freedom. The carriage rolls side-to-side on a steel pipe, but also tilts on that pipe. A thinner shaft (highlighted in red) also allows the router and follower to pivot.
The most complicated parts for the carriage are the "side arms". I used my BigPrint program to make the 1:1 printouts, which I used as paper templates to cut them out. I only used a few dabs of glue to attach them. That makes them easier to get off again.
I used an awl to punch divots through all the hole center marks. Best to do that right away so I don't forget later.
I highly recommend using baltic birch plywood. It's made with thin layers of birch throughout. A quarter sheet (2'x4') will be about four times as much wood as you need. You can find the quarter sheets of birch plywood with the "handy panels" at Home Depot.
The screw thread should only engage the bottom half of the arm, so that when the screw is tightened, it pulls the end of the arm together. I'm using a larger drill (5/32") to expand the top part of the hole. Here's checking the depth that I need to drill this to.
I cut the router mounting hole with the bandsaw. I could just cut in from the outside because I need to cut a gap in the circle anyway. Easier and more accurate than trying to do it with a scroll saw or a circle cutter on the drill press.
The hole was sized very tight - too tight, so that I could hardly force the router into it. The aluminium from the router left some black marks on the wood, and that tells me where I need to cut away a bit more material. I'm just using the side of the bandsaw blade to graze away at the wood where I see dark marks.
Bearing mountsThe guide bearings will get mounted to a piece of wood that fits into the slots of the side arms.
Please note - this is not a plumbing pipe. If you use plumbing pipe, you have to make minor adjustments to where the bearings are mounted to accommodate the large diameter.
Do not use copper or aluminium piping - it's too flexible.
If you use plumbing pipe (~22 mm diameter), mount each bearing 1 mm further away from the pipe to maintain the same center line.