J.W. Done makes an interesting tool for deburring internal cross holes: the Orbitool. As you may know, when two holes are drilled into one another there’s usually a nasty burr that can be very hard to remove. The common solution is steel or abrasive brushes; however, those can negatively affect bore finish and diameter.
The tool is a half round bur with the largest diameter at the end of the tool and a polished collar around the periphery. In use it’s inserted into the hole and pressed against the wall of the hole. When it reaches the cross hole the machine revolves the tool (or the part is revolved around the tool) filing away the burr at the intersection of the holes. They show both manual and automatic usage in their YouTube videos. They also offer carbide and abrasive-headed tools that operate on the same principle. There’s a detailed test report (.pdf) that shows the results obtained in a range tests.
Has anyone out there had the opportunity to use this tool? Looks like a great way to deal with a common problem in all sorts of manufacturing and hobby metalwork.