EDM Drilling

EDM drilling rapidly produces small, deep start holes in conductive hard materials using a tubular electrode, with minimal cutting forces and high aspect ratios.

Overview

EDM drilling (small hole EDM, hole popper, fast hole EDM) burns small-diameter holes in electrically conductive materials using a rotating tubular electrode and pressurized dielectric. It excels at making deep, straight start holes for wire EDM, and at drilling through hardened tool steels, carbide, and superalloys without tool deflection or cutting forces.

Choose EDM drilling for high aspect ratio holes (often 10:1 to 30:1+), difficult-to-machine hardness, and when you need reliable through-holes in tough materials. Tradeoffs: hole size is limited by electrode diameter, finish is typically rougher than reamed/drilled holes, and there can be a recast/heat-affected layer that may need secondary processing for fatigue-critical parts. Expect slower rates as diameter grows, and plan for electrode wear and slight taper depending on depth and flushing.

Common Materials

  • H13 tool steel
  • D2 tool steel
  • Inconel 718
  • Titanium Ti-6Al-4V
  • Tungsten carbide
  • Stainless steel 17-4 PH

Tolerances

±0.002"

Applications

  • Wire EDM start holes in hardened dies and punches
  • Cooling holes in turbine and hot-section components
  • Ejector pin vent holes in injection molds
  • Cross-holes in hardened shafts and valve components
  • Broken tap/drill removal via burn-out
  • Pilot holes for EDM slotting in carbide tooling

When to Choose EDM Drilling

EDM drilling fits parts that need small-diameter, deep holes in electrically conductive materials, especially when the material is hardened or tough. It’s a strong choice for prototype to low-volume production where repeatable hole location and depth matter more than a smooth, reamed finish. It also works well as a preparatory step when downstream processes require a precise start hole.

vs Sinker EDM

Choose EDM drilling when you need high-aspect-ratio round holes fast, especially for start holes and through-holes. Sinker EDM is better for shaped cavities; EDM drilling is optimized for small, deep bores with simpler programming and typically higher drilling throughput.

vs Wire EDM

Choose EDM drilling when the primary need is a start hole or a deep small hole rather than a profile cut. Wire EDM can’t begin without a start hole on closed features, and it’s inefficient for producing many small deep holes compared to a dedicated hole-drilling EDM setup.

vs Gun drilling

Choose EDM drilling for hardened steels, carbide, and superalloys where mechanical drilling risks tool breakage, wander, or excessive burrs. Gun drilling can deliver better surface finish and larger diameters efficiently in machinable materials, but struggles as hardness and tool wear rise.

vs Laser drilling

Choose EDM drilling when you need straighter holes with controlled diameter in thicker sections and want to avoid laser taper and spatter on many alloys. Laser drilling wins on very small diameters and very high hole counts in thin sections, but can have more thermal effects and geometry variability in deeper holes.

Design Considerations

  • Specify hole diameter range and tolerance; small changes in diameter can change feasible electrode options and cycle time
  • Call out maximum acceptable taper and whether the hole must be straight through or can have a small entrance/exit condition
  • Define recast/HAZ requirements (allowed, removal depth, or post-process like ream/hone/EDM skim) for fatigue- or sealing-critical holes
  • Provide material condition (annealed vs hardened, hardness value) and thickness at the hole location for accurate quoting
  • Add a small land/flat at the entry if possible to improve location accuracy and reduce electrode walk on curved surfaces
  • State whether the hole is a wire-EDM start hole vs a functional flow/sealing feature; it changes inspection and finish expectations