Will,
I commend you for your circumspection on this process, but I have found that it really is pretty basic if you have the right equipment, and it sounds like you do.
To level your bearing edge, glue sheets of sandpaper to a flat surface. Usually, glass or marble are ideal, but I have used 3/4” MDF or plywood with success. The grit of the sandpaper will depend on the condition of the bearing edge prior to your repair. For a bearing edge that only has some small nicks or imperfections, 150 grit is a good starting point. Make sure you have enough sheets glued down to support the shell fully as it sits. Do not push of pull the shell across the sandpaper. Instead, rotate it back and forth a few times, reposition it, then repeat. You want to avoid keeping it in just one single orientation, because as hard as you try not to, you will sand one side more than another. Repeat this process until you have a shell edge that sits flat without allowing light to escape when you place a light source inside and view it from an oblique angle from the outside
There are many spray adhesives you can buy that allow for temporary adhesion to a substrate. You can temporarily apply the sandpaper or leave it in place for the next drum..
As you know, a table-mounted router bit with a bearing will follow the contours of your workpiece (the drum shell), so you need to ensure that the interior of the shell that will be in contact with the bearing is smooth. If there are any chips or missing pieces of inner ply, your router cut will reflect that. Take the time to repair such areas first. A good quality wood filler will work fine. You will need to sand this by hand.
My router table has a relatively small footprint, so I made it larger by cutting a hole in a quarter sheet of plywood for the router bit and bolted it to the table. Use whatever you have that will reliably provide a smooth flat surface but still allow your router bit to peek up through high enough to do the job.
Start your bearing cuts on the router table with the bit low. Rotate the shell into the cutter slowly, but not so slow as to burn. When you need to shift hand position, you may find it advantageous to slide the shell away from the bit while you shift hand position, then re-engage.
Finish up with light hand sanding with fine grit paper.
You will be fine!
Josh
