Abstract: A self-calibrating countersink tool includes a reusable insert-holder with an axis-defining shank portion and an insert-receiving notch disposed at one end of the holder. The tool also includes at least one selectively attachable insert which is sized and shaped to be received within the insert-receiving notch of the holder. Each disposable insert includes a tapered cutting-edge portion and a notch-mating portion which is complementary in shape to the insert-receiving notch. When the insert is in mating engagement with the holder, the cutting-edge of the insert is disposed forwardly of the holder and defines an angle of between about 105 and 165 degrees relative to the holder axis. The countersink tool also includes an affixation means for affixing a disposable insert to the holder such that the insert is in mating engagement with the insert-receiving notch.

Abstract: Electrical feedthrough seal, such as a glass-to-metal seal, including a protective ceramic body which shields at least portions of the inner surfaces of the glass seal. The ceramic body is preferably disposed about the lead-wire of the feedthrough.

Abstract: Use of niobium coatings in brazing ceramic and metal bodies particularly for forming hermetic ceramic-metal seals.