When I built the torsion box table that my CNC sits on I included an area w/o ribs so I could add a vertical fence for cutting finger joints and dovetails. I finally got around to building and installing one earlier this week. The design is off Etsy. I would have preferred something even wider but this will be fine for now. To prove that it was worth doing at all, I started by cutting a small hole in the top off to the side and installed a small fence. Then I proceeded to cut some fingers in a couple of boards. With just one allowance adjustment of the toolpath I had nice crisp joints that fit very well.
With that a success I proceed to build the new fence.
The design is pretty clever, and it went together pretty easily after I added some allowance for the mortise/tenon joints. It's held together with just a couple of screws on each side. The plan has the provision for dog holes, too, but I left them out. I'll use the T-nuts I installed on the back to hold whatever fences and stops I need.
I cut the hole in the table top with the CNC to assure that the fence would end up parallel with the X-rail. The fence is bolted to the table top. It's as square vertically as I can measure.
To finish, I machined a removable plug to fill the hole in the top, and added used the offcut from the new spoilboard on top. It's held in place from the bottom and is easily removed for use of the fence. After installing and flattening the new spoilboard it's done.
I can already see this is going to be a little inconvenient to use, having to reach my hand down through the top to tighten the clamps (yet to be added), or from under the table. I originally had thought about making the table top a U shape and installing the vertical fence at the back of that, with all of it as far forward as possible. But I didn't want to risk compromising the stiffness of the table so I didn't. Now that I've used the table for a year or so I see that it's incredibly stiff and would remain so. So if I end up using the vertical fence enough to justify the time to do so, I will cut the top in that C shape. I'll also make the fence wider at the same time, and likely add a tilt feature to allow cutting joinery on inclined parts. As OneFinity says in their marketing slogan, infinite possibilities.
John