by Bernard Martin
When manufacturers need to produce holes in a workpiece, the first instinct is almost always to reach for a conventional drill. After all, drilling is one of the oldest and most efficient machining operations in manufacturing. Modern CNC machining centers and drill presses can produce thousands of accurate holes every day at a remarkably low cost.
Yet there are applications where conventional drilling reaches its practical limits. Extremely hard materials, ultra-small hole diameters, deep holes with high aspect ratios, and delicate workpieces can quickly turn a routine drilling operation into a costly challenge. In these situations, Electrical Discharge Machining (EDM) hole drilling offers an entirely different approach.
So, which process is better?
The answer is the same one experienced manufacturing engineers often give to complex machining questions: it depends on the application.
Understanding where each process excels—and where it begins to struggle—allows manufacturers to select the most efficient, economical, and reliable solution for the job.
Conventional Drilling: The Production Workhorse
Conventional drilling removes material mechanically. As the drill rotates, its cutting edges shear material away while chips are evacuated from the hole.
For most applications, this remains the fastest and most economical way to produce holes.
Conventional drilling is ideal for:
- General-purpose production machining
- Aluminum, mild steel, cast iron, and stainless steel
- Moderate hole depths
- Larger diameter holes
- High-volume manufacturing
- Low cost per hole
Modern carbide drills, coolant-through tooling, and high-performance coatings have dramatically expanded what conventional drilling can accomplish. Today's machining centers routinely produce thousands of precision holes with excellent repeatability.
For many manufacturers, conventional drilling is—and should remain—the first choice.
Where Conventional Drilling Begins to Struggle
Every machining process has limitations.
As hole diameters become smaller, depths increase, or materials become more difficult to machine, conventional drilling introduces challenges that can impact productivity and part quality.
These challenges often include:
- Tool deflection
- Drill breakage
- Excessive tool wear
- Burr formation
- Heat generation
- Difficult chip evacuation
- Reduced accuracy in deep holes
The problem becomes even greater when machining hardened tool steels, carbide, titanium, Inconel, or other high-strength alloys. While advances in cutting tools continue to push these boundaries, there are still applications where cutting simply becomes impractical.
This is where EDM hole drilling enters the conversation.
How EDM Hole Drilling Works
Unlike conventional drilling, EDM hole drilling removes material without cutting it.
Instead, a small tubular electrode creates thousands of controlled electrical discharges between the electrode and the workpiece. Each spark erodes a microscopic amount of material while dielectric water continuously flushes debris from the hole.
One of the biggest advantages of the process is that the electrode never physically contacts the workpiece. Because there are virtually no cutting forces, EDM hole drilling eliminates many of the problems associated with conventional drilling.
The process is capable of producing precise holes in electrically conductive materials regardless of their hardness.
When EDM Hole Drilling Is the Better Choice
Rather than replacing conventional drilling, EDM hole drilling fills the gaps where conventional machining becomes difficult or inefficient.
Machining Hardened Materials
Heat-treated tool steels, carbide, titanium, and nickel-based superalloys often present significant challenges for traditional drills.
Because EDM relies on electrical discharge rather than cutting forces, material hardness has relatively little influence on the machining process. This allows manufacturers to produce holes in materials that would quickly destroy conventional cutting tools.
Producing Extremely Small Holes
As drill diameters decrease, tool fragility increases dramatically.
Producing holes only a few tenths of a millimeter in diameter with conventional tooling requires exceptional care and often results in frequent drill breakage.
EDM hole drilling routinely produces these small-diameter holes with excellent consistency.
Deep Hole Applications
Deep holes create problems for any cutting process.
Chip evacuation becomes increasingly difficult, coolant struggles to reach the cutting edge, and long drills become susceptible to deflection.
EDM hole drilling continuously flushes debris through the hollow electrode, making it well suited for high aspect ratio holes that would challenge conventional drilling.
Wire EDM Start Holes
One of the most common applications for EDM hole drilling is creating start holes for Wire EDM.
Before a wire can begin cutting an internal profile, it must first pass through the workpiece. Fast-hole EDM machines provide these precision starting holes quickly and accurately while minimizing setup time.
Many mold shops and precision manufacturers consider an EDM hole drilling machine an essential companion to their Wire EDM equipment.
Broken Tap Removal
Anyone who has broken a tap inside an expensive workpiece understands how quickly a simple mistake can become costly.
EDM hole drilling can erode the broken tap without damaging the surrounding material, often saving parts that might otherwise be scrapped.
Conventional Drilling vs. EDM Hole Drilling
Conventional Drilling | EDM Hole Drilling |
|---|---|
| Removes material by cutting | Removes material through electrical discharge |
| Generates cutting forces | Virtually no cutting forces |
| Tool wear increases with material hardness | Material hardness has minimal effect |
| Limited by chip evacuation | Continuous flushing through electrode |
| Burrs may require secondary operations | Minimal burr formation |
| Deep holes become increasingly difficult | Excellent for high aspect ratio holes |
| Best for general production | Best for specialized applications |
| Lower cost per hole for standard work | Excels where conventional drilling reaches its limits |
Neither process is universally better. Each has applications where it delivers the greatest value.
Why Many Shops Invest in Both Technologies
One of the biggest misconceptions surrounding EDM hole drilling is that it replaces conventional drilling.
In reality, the opposite is true.
Most successful manufacturers use each process where it provides the greatest advantage.
Conventional drilling handles the overwhelming majority of production holes quickly and economically.
EDM hole drilling solves the difficult jobs—those involving hardened materials, deep holes, broken taps, intricate components, or Wire EDM start holes—that conventional drilling cannot perform efficiently.
Rather than competing with one another, the two technologies complement each other.
Ocean River EDM Hole Drilling Machines
For manufacturers looking to add EDM hole drilling capabilities, Ocean River offers a range of compact, high-precision machines designed for mold shops, toolrooms, aerospace suppliers, medical manufacturers, and general job shops.
Among the most versatile models are the River 3 and River 35, both of which combine a compact footprint with CNC positioning and precision EDM drilling capabilities.
Ocean River River 3
The Ocean River River 3 is an excellent entry point for shops adding EDM hole drilling capability.
Its 300 × 200 mm X-Y travel, 350 × 250 mm worktable, and workpiece capacity of up to 150 kg make it well suited for mold components, fixtures, precision tooling, and Wire EDM start-hole applications. The machine accommodates electrodes ranging from approximately 0.2 mm to 3.0 mm, allowing manufacturers to produce exceptionally small holes with high accuracy.
For many job shops, the River 3 provides the capability to machine applications that would otherwise require outsourcing.
Ocean River River 35
For larger workpieces and more demanding applications, the River 35 expands both capacity and flexibility.
The machine offers a larger work envelope, accommodates workpieces up to 250 kg, and is available with an optional ±45° tilting head that enables angled-hole drilling without complex fixtures or secondary setups. This capability is particularly valuable for components requiring intersecting passages or holes that cannot be reached with a vertical spindle alone.
The River 35 delivers the same precision EDM drilling capabilities while providing additional capacity for manufacturers producing larger molds, dies, aerospace components, and industrial tooling.
Intelligent Controls Designed for Productivity
A machine's mechanical construction is only part of the equation. Productivity also depends on how quickly operators can program jobs, set up workpieces, and monitor machining.
Ocean's controller includes features designed to simplify operation, including conversational programming, DXF file import with graphical simulation, workpiece rotation correction, machining parameter management, real-time sparking waveform monitoring, and optional breakthrough detection that automatically manages machining depth after the hole is pierced. These capabilities reduce setup time while helping operators achieve consistent results across a wide range of applications.
Choosing the Right Process
Manufacturing is rarely about finding a single "best" process. Instead, it is about selecting the process that delivers the best combination of productivity, quality, and cost for a specific application.
For standard production drilling in machinable materials, conventional drilling remains the clear choice. It is fast, economical, and highly efficient.
However, when applications involve hardened materials, extremely small diameters, deep holes, Wire EDM start holes, or broken tap removal, EDM hole drilling offers capabilities that conventional cutting tools simply cannot match.
The question isn't whether one process is superior to the other.
The real question is whether your application has reached the point where conventional drilling is no longer the most efficient solution.
For many manufacturers, adding an EDM hole drilling machine such as the Ocean River River 3 or River 35 doesn't replace existing machining capabilities—it expands them, opening the door to new applications, greater flexibility, and the confidence to tackle jobs that were once considered too difficult or too risky.