Appearance
The cheapest hole-making technology depends entirely on diameter, material, depth, and volume. Gun drilling dominates one corner of the cost map, laser drilling another, and EDM occupies the narrow middle — each with a clear economic boundary.
Cost Comparison Summary
| Cost Factor | Gun Drilling | EDM Drilling | Laser Drilling |
|---|---|---|---|
| Equipment cost | Low | Medium | High |
| Tool/electrode wear | High | Medium | None |
| Processing speed | Medium | Slow | Fast |
| Per-hole cost (low volume) | Low | Medium | High |
| Per-hole cost (high volume) | Medium | High | Low |
| Setup cost per job | Low | Medium | Low |
| Maintenance cost | Moderate | Moderate | Low |
Equipment Investment
Gun drilling has the lowest entry cost — a basic gundrilling machine starts at approximately $50,000–100,000, and gun drilling can also be performed on standard CNC machines with high-pressure coolant.
EDM drilling machines start at approximately $80,000–200,000 for basic machines and $300,000+ for multi-axis CNC systems. The dielectric fluid system and filtration add ongoing operational cost.
Laser drilling systems start at $200,000–500,000 for industrial nanosecond pulse systems and exceed $1,000,000 for femtosecond or picosecond precision systems. The high capital cost is the primary barrier to adoption.
Consumable and Tooling Cost
Gun drilling consumable cost is dominated by tool wear. A solid carbide gun drill costs $50–500 depending on diameter, and micro-drills for sub-0.1 mm holes cost $10–50 each with frequent breakage. Each regrind removes 0.3–0.5 mm of tool length, and a drill can be reground 15–25 times before replacement. The effective cost per cutting edge is low for large diameters but high for micro-drilling.
EDM consumable cost comes from electrode wear. Copper, graphite, or tungsten electrodes wear during the spark erosion process and require dressing or replacement. Electrode breakage in small-hole EDM adds significant cost. Dielectric fluid filtration and replacement are ongoing expenses.
Laser drilling has zero tool wear. The only consumables are assist gas (oxygen, nitrogen, argon) and electrical power. This is the single largest economic advantage of laser drilling at production volumes.
Processing Speed and Throughput
| Technology | Typical Speed | Relative Throughput |
|---|---|---|
| Gun drilling | ~20 holes/min (0.1 mm dia) | Medium |
| EDM drilling | < 1 hole/min (deep holes) | Low |
| Laser drilling | Up to 2,000 holes/min (0.2 mm dia) | High |
Throughput directly affects per-hole labour and overhead cost. Laser drilling's speed advantage grows with hole count, making it the lowest per-hole cost option for high-volume micro-hole applications despite the highest equipment investment.
Deep Hole Capability (L/D > 10:1)
For deep holes specifically, the cost comparison shifts:
- Gun drilling (up to 400:1 L/D): Lowest cost for deep holes in conventional metals (steel, aluminium) at diameters above 0.5 mm. The process was designed for deep holes, and the cost advantage compounds with depth.
- EDM drilling (up to 20:1 L/D): Cost increases sharply with depth. Electrode wear and slow material removal make deep-hole EDM uneconomical compared to gun drilling when both are technically feasible.
- Laser drilling (up to 50:1+ L/D): Competitive for very small diameters (< 0.5 mm) at high L/D, particularly in hard or brittle materials where gun drilling is not feasible.
Material Effects on Cost
| Material | Cheapest Method | Reason |
|---|---|---|
| Aluminium | Gun drilling | Fast cutting, low tool wear |
| Carbon steel | Gun drilling | Standard production |
| Stainless steel | Gun drilling | Moderate tool wear, acceptable |
| Titanium | Gun drilling | Higher tool wear but still economic |
| Inconel / superalloys | EDM or laser | Gun drill wear is prohibitive |
| Carbide / hardened tool steel | EDM | Gun drilling impossible |
| Ceramics / glass | Laser | Only feasible option |
| Composites | Gun drilling or laser | Material-dependent |
Hybrid Process Economics
Combining technologies often produces better economics than any single method:
| Hybrid Approach | Cost Improvement | Application |
|---|---|---|
| Laser pilot + EDM finish | 42% cost reduction vs EDM alone | Fuel injection nozzles |
| Laser pre-drill + gun drill finish | 2.5–4.3× tool life improvement | Inconel 718 cooling holes |
| Gun drill rough + EDM finish | Reduced EDM time | Mould cooling channels |
The sequential laser + EDM process (Li et al.) achieved a 42% cost reduction and 90% increase in production capacity compared to EDM alone by using the laser for bulk material removal and EDM only for finishing.
Selection Framework by Application
| Application | Recommended Method | Rationale |
|---|---|---|
| Cooling holes in turbine blades | Laser drilling | Sub-mm diameter, Inconel, high volume |
| Fuel injector passages | Gun drilling or hybrid | 1–3 mm, steel, moderate volume |
| Mould cooling channels | Gun drilling | 6–20 mm, steel, deep holes |
| Diesel injector nozzles | Hybrid laser + EDM | Small diameter, high precision |
| Printed circuit board vias | Laser drilling | Sub-0.1 mm, non-conductive substrate |
| Hydraulic valve bores | Gun drilling | 5–30 mm, steel, production volumes |
| Medical stent features | Laser drilling | Sub-mm, high precision, no HAZ |
| Watch jewel bearings | Laser drilling | Sub-mm, ceramic |
FAQ
Which hole-making method has the lowest equipment cost?
Gun drilling. Basic machines start at $50,000–100,000. EDM costs $80,000–300,000. Laser drilling costs $200,000–1,000,000+.
Which method has the lowest per-hole cost at high volume?
Laser drilling. Despite the highest equipment cost, zero tool wear and extremely high speed (up to 2,000 holes/min) make per-hole cost the lowest at production scale.
Is gun drilling cheaper than EDM?
For deep holes (L/D > 10:1) in conventional metals, yes — significantly. Gun drilling removes material much faster and has lower setup cost. EDM is only competitive when the material cannot be drilled mechanically.
What is the most cost-effective way to drill deep holes in Inconel?
Laser pre-drilling followed by gun drilling. This hybrid approach improves tool life by 2.5–4.3× and reduces thrust forces by 57% compared to gun drilling alone.
Does laser drilling have tool wear?
No. Laser drilling is a non-contact process with zero tool wear. Consumables are limited to assist gas and electrical power.
Can EDM drill deep holes economically?
Only up to approximately 20:1 L/D and only in conductive materials. Costs increase sharply with depth due to electrode wear and slow material removal.
What is the cost advantage of hybrid laser + EDM?
Research shows a 42% cost reduction and 90% production capacity increase compared to EDM alone for fuel injection nozzle applications.
When does gun drilling become uneconomical?
Gun drilling becomes uneconomical below approximately 0.5 mm diameter (tool breakage cost), above approximately 45 HRC hardness (tool wear), or in non-conductive materials.
Which technology is best for sub-50 µm holes?
Laser drilling. Mechanical drilling below 50 µm is impractical due to tool breakage. EDM can drill sub-50 µm holes but only in conductive materials and at lower speed.
How does depth affect the cost comparison?
Gun drilling cost scales linearly with depth. EDM cost scales super-linearly with depth (slower removal at depth). Laser drilling cost is largely independent of depth within its L/D capability.
Conclusion
The cost ranking of deep hole drilling vs EDM vs laser drilling reverses depending on the application. Gun drilling has the lowest entry cost and lowest per-hole cost for deep holes in conventional metals — it dominates the largest segment of the market. Laser drilling has the highest entry cost but the lowest per-hole cost at high volume with zero tool wear, making it the economic winner for micro-holes, hard materials, and high-volume production. EDM is the most expensive per hole but is irreplaceable for hard conductive materials where gun drilling is not feasible and laser drilling cannot meet finish requirements. Hybrid processes that combine methods sequentially often achieve the best cost balance for demanding applications.