This stick is Oak its approximately 3/4" square. I used a regular old hand saw to cut the groove. The groove should be cut across the grain to keep the wood from splitting. You'll wana cut the groove only a CH deeper than the rim, if you cut the groove to deep its more likely to split the stick. If the saw kerf is to narrow you can use sand paper to make it wider.
Go real slow so you dont move the metal around any more than you have to, the more it moves the the more it loses. Whatever you do, especially on a badly damaged rim, do not try to bend the metal all the way to its original position in one bend....you gota work slow & easy, and go back a couple times and re-bend it til its reached a satisfactory shape. Theres a possibility the metal was stretched, especially if the rim was bent out and not in, when the rim was bent. If thats the case good luck because once its stretched youll never get it to shrink with out heating it red hot and quenching it.
Theres no way to keep from losing a little porcelain when your straightening the rim.