The principle benefits of EDM—its excellent surface finish, minimal heat-affected zone (HAZ) and ability to cut hardened materials and exotic alloys—make it ideal for certain hole-making applications. If a small pilot hole is pre-drilled into workpiece, wire can be threaded through it to complete the operation using wire EDM.
Cases where this is impossible—blind hole applications, for example—call for a specialized EDM hole making machine. Commonly called a “hole popper” this machine uses a rotating conductive tube for its electrode and a continuous flow of dielectric fluid (usually deionized water) to flush the cut. Hole popper EDM can also be used to create the pilot hole necessary for wire threading.
The ability to create accurate and precise holes, even in hardened or exotic materials has been a key development for several advanced technologies, such as EDM-created cooling holes in high-temperature alloy turbine blade sections. This permits a “film cooling” process, which allows jet engines to operate at higher temperatures for greater durability and efficiency.