What type of EDM machine is typically used for machining internal holes?

Sinker EDM is the correct choice for machining internal holes because it utilizes a specially shaped electrode to create precise features, including complex internal geometries and cavities. The process involves creating an electrical discharge between the electrode and the workpiece, which erodes the metal based on the shape of the electrode. This method is particularly effective for producing intricate shapes that cannot be easily achieved with traditional machining methods.

Wire EDM, while also effective for precision cutting, is typically used for creating external shapes and profiles rather than direct internal holes. It involves moving a thin wire through the workpiece to cut it, which is not suitable for creating enclosed internal features. Laser EDM and Plasma EDM are less common for machining internal holes. Laser EDM utilizes focused laser beams for cutting and may be more suited for surface cutting rather than creating internal features, while Plasma EDM employs high-temperature plasma for cutting metals and is generally not adapted for precision internal hole machining.