30-Second Summary: The core logic of equipment selection — first determine the process method, then specify the machine specifications. The most expensive machine is not necessarily the best; the best machine is the one that matches the process requirements of your dominant products. Key decision parameters: maximum bore diameter and depth, spindle power, coolant system pressure/flow, workpiece clamping method, and automation requirements.
Machine Type Comparison
| Type | Applicable Process | Depth Capacity | Accuracy | Reference Price |
|---|
| Gundrill dedicated machine | Gundrilling | ≤ 3m | High | $50-150k |
| BTA dedicated machine | BTA/trepanning/pull boring | ≤ 12m (up to 20m special) | High | $100-500k+ |
| Retrofitted machining center | Ejector drilling/extended drill | ≤ 1.5m | Moderate | Depends on base machine |
| Horizontal deep hole drilling machine | Gundrill/BTA | ≤ 6m (up to 20m custom) | Highest | $150-600k |
| Vertical deep hole drilling machine | Gundrill | ≤ 2m | High | $50-200k |
Key Selection Parameters
- Maximum bore diameter and depth: Determines machining range. Gun drilling covers 1-50 mm; BTA covers 12-250+ mm.
- Spindle power: Insufficient power limits feed rate. General range: 7.5-30 kW for gun drilling, 15-100+ kW for BTA. Calculate net power using cutting force models from tool manufacturers' handbooks.
- Coolant system pressure/flow rate: Gun drilling typically requires 25-60 bar at 10-100 L/min; BTA requires 5-20 bar at 40-200+ L/min. High-end systems can reach 170 bar.
- Workpiece clamping method: Rotating workpiece (for shafts) vs. fixed workpiece (for complex shapes). Rotating workpieces generally produce better straightness due to counter-rotation capability.
- Automation and auxiliary features: Automatic loading/unloading, tool monitoring, chip conveyor system, coolant filtration.
Coolant System Specification Guide
| Process Method | Pressure Range | Flow Rate Range | Filtration Requirement | Coolant Type |
|---|
| Gun drilling (< 10 mm) | 30-60 bar | 10-40 L/min | < 10 μm | Oil or high-concentration emulsion |
| Gun drilling (10-50 mm) | 25-50 bar | 40-100 L/min | < 20 μm | Oil or emulsion |
| BTA/STS (12-70 mm) | 10-30 bar | 100-400 L/min | < 50 μm | Emulsion or oil |
| Ejector/DTS (20-250 mm) | 5-20 bar | 200-800 L/min | < 100 μm | Emulsion standard |
Machine Configuration Types
| Configuration | Pros | Cons | Best For |
|---|
| Horizontal | Best rigidity, long stroke, gravity chip evacuation, unlimited workpiece length | Large floor space, higher cost, coolant return requires trench/pump | Shafts, long bores (bars, cylinders), high-production |
| Vertical | Small footprint, easy alignment (gravity assists), no coolant return pump needed | Limited stroke (typically ≤2m), not for very long holes, workpiece height restricts ceiling | Precision small holes, valve bodies, limited floor space |
| CNC retrofit | Highest flexibility, leverages existing equipment investment | L/D limited to ~30:1, needs ≥70 bar coolant system added, reduced rigidity vs. dedicated machine | Small batches, multi-variety, job shops, prototype work |
Major Equipment Brands
- UNISIG (USA): High-end deep hole drilling machines, bore 25-300mm, depth up to 12m. Strong in automation and multi-spindle cells.
- TBT (Germany): Tiefbohrtechnik — one of the global market leaders. Full range of deep hole drilling machines and tooling.
- Mollart Engineering (UK): Custom deep hole drilling machines, exclusive UK partner of Botek tooling. Strong in automotive and defense.
- Precihole (India): Φ1-250mm, depth up to 10m, good value for mid-range requirements.
- Botek (Germany): Focused on deep hole tooling (gundrills, BTA heads, ejector drills), also offers machine retrofit solutions. Tool diameters from 0.5 mm to 500 mm.
- Kays Engineering (UK): Custom deep hole drilling machines, among the global top 5 market share.
- Entrust / TechniDrill: Specialized deep hole machine builders serving the global market.
- Sunnen (USA): Leader in skive & roller burnishing and honing equipment.
- Galbiati Group (Italy), Honge Precision (China), Dezhou Guanlu / Jutai (China): Regional suppliers offering cost-effective solutions.
💡 Selection process: 1. Define product mix (bore diameter, depth, material, batch size) — 2. Determine process method (gundrill vs. BTA vs. ejector) — 3. Calculate required spindle power using Vc and feed from material guide — 4. Size coolant system (pressure + flow) using manufacturer charts — 5. Select machine configuration (horizontal vs. vertical) based on workpiece geometry — 6. Evaluate automation level based on batch size.