Abstract: When drilling very small diameter holes in workpieces, there is a great tendency for expulsed workpiece material to travel back along the electron beam path, and to deposit as debris within the interior of the gun. The debris is caused to mostly land at a recess in the rim of a rotatable interior shield, positioned adjacent the beam path inside the gun. The deflection angle of the electron beam is precisely adjusted so that the expulsed workpiece material lands in the recess, from when it is removed by a scraper. A tab is placed within the recess at the rim of the shield, and helps remove small amounts of deposit which still adhere to stationary parts of the electron beam gun system adjacent to the shield. In this embodiment, a resilient scraper such as a wire brush, is used to remove adhering debris from the rim of the shield.

Abstract: Disclosed is a method and fixture for applying a thin layer of polymer material to a piece of wavy sheet metal, so that the layer may function as a backer during electron beam drilling. The sheet is drawn to the smooth surface of a fixture using a vacuum, and polymer is flowed across the surface using a curved leveling board, which produces a generally uniform thickness molding. The edges of the backer are molded with a bevel edge by shaped side rails, to provide a relief around the edge of the backer layer. Thus a raised up portion usually occuring at the edge rail will not interfere with the precise spacing which the backer is intended to produce between the sheet and the workpiece holder during electron beam drilling.

Abstract: Disclosed is an electron beam hole drilling process in which the workpiece surface where the hole exits is covered with a backer comprising particulate bonded to itself and the exit surface by a binding agent. The backer enables a hole having substantial uniform symmetry along its length to be drilled and is particularly useful for hollow parts and contoured surfaces. Backers removable by liquifying, melting dissolution, leaching and the like, are particularly useful for inaccessible exit surfaces. In a preferred embodiment the backer is comprised of a nonmetallic particulate such as glass while the binder is a soluble silicate.

Abstract: Disclosed is an electron beam drilling process in which the workpiece surface first penetrated by the beam is coated with a stop-off material having the required high temperature resistance for preventing formation of burrs around the perimeter of the hole from hot molten spatter which is ejected from the entrance to the hole during the drilling operation. A preferred stop-off material is a substantially continuous layer of boron nitride on the first penetrated surface of the workpiece.