Well, I do believe this might just work. Found a scrap of maple and gave it a test.
Drilled out the center with a spade bit then Went part way down from the top with a router collar.
Then took it out, put it in a vise and cleared out from the other end with a bottom bearing bit.
A little burning on the corners, but it's hidden so not a huge deal.
Gave it a half hearted attempt to square it up and I'll be darned if it didn't clear it out pretty easy.
I think this will work.
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