To polish the port I used the blunt end of a drill in a battery drill, some metal polish & some hours of my life. The chamfer I do through the compression tube with an old 6mm drill (ie. blunt) welded to a long rod & I go very carefully, then I deburr by running it backwards. I tried a new drill the first time & it tried to give me a 6mm transfer port...

If anyone has any other suggestions on the subject I would be very pleased to hear them.