Every so often I encounter the problem of putting a roundover on thin stock. In this case I was making a custom sized drawer organizer for someone, and the dividers are Baltic Birch ply just under 1/4", probably 6mm or so. I have roundover bits in small radii, 1/8", 3/16", 1/4". The bearing on these bits will hit the stock on the first pass, but when flipped over they will not find a bearing surface without ruining the roundover. Plus in my experience when near the edge of the bearing, the damn washer has a habit of leaving a scoring mark in the workpiece.
So just use the fence on the router table instead of the bearing, right?
Well what if the workpiece is curved?
My quick solution was to take a piece of scrap MDF, drill a hole just larger than the bearing, secure it to the router table with a few dabs of hot glue located so the jig face was just a hair proud of the bearing. I raised the bit into the jig so it would be zero clearance and done. The bearing and the damn washer are buried in the jig and the whole operation was pretty safe. The jig took about 5 minutes to fabricate.
Note: if it had been a very critical component, I might make the jig a radius to match the workpiece instead of a protruding "finger". In this case I would have had to make two jigs because the dividers were two different curves because one row is longer than the other, but this single point jig worked fine for the task. It would work fine for a single pass round over using a beading bit also.
Sharing this technique for anyone else encountering the same problem. If others have different ways of solving this issue, I'm interested to learn about alternatives.
Ed Santos
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